[PATCHv4/RFC 2/3] gitweb: Incremental blame (WIP)

[Jakub Narebski <jnareb@gmail.com>]

This is tweaked up version of Petr Baudis <pasky@suse.cz> patch, which
in turn was tweaked up version of Fredrik Kuivinen <frekui@gmail.com>'s
proof of concept patch.  It adds 'blame_incremental' view, which
incrementally displays line data in blame view using JavaScript (AJAX).

This patch does not (contrary to the one by Petr Baudis) enable this
view in gitweb: there are no links leading to 'blame_incremental'
action.  You would have to generate URL 'by hand' (e.g. changing 'blame'
or 'blob' in gitweb URL to 'blame_incremental').  Having links in gitweb
lead to this new action (e.g. by rewriting them like in previous patch,
if JavaScript is enabled in browser) is left for later.

Like earlier patch by Per Baudis it avoids code duplication, but it goes
one step further and use git_blame_common for ordinary blame view, for
incremental blame, and (which is change from previous patch) for
incremental blame data.

How the 'blame_incremental' view works:
* gitweb generates initial info by putting file contents (from
  git-cat-file) together with line numbers in blame table
* then gitweb makes web browser JavaScript engine call startBlame()
  function from blame.js
* startBlame() opens connection to 'blame_data' view, which in turn
  calls "git blame --incremental" for a file, and streams output of
  git-blame to JavaScript (blame.js)
* blame.js updates line info in blame view, coloring it, and updating
  progress info; note that it has to use 3 colors to ensure that
  different neighboring groups have different styles
* when 'blame_data' ends, and blame.js finishes updating line info,
  it fixes colors to match (as far as possible) ordinary 'blame' view,
  and updates generating time info.

It deals with streamed 'blame_data' server error by notifying about them
in the progress info area (just in case).

Differences between 'blame_incremental' and original 'blame' view:
* 'blame_incremental' always used (partial) query form for links
  generated by JavaScript.  The difference is visible if we use path_info
  link (pass some or all arguments in path_info), e.g. in 'blame' view
  called using:
    http://git.example.com/w/git.git/blame/HEAD:/README
  we have 'linenr' links using the same form:
    http://git.example.com/w/git.git/blame/e83c5163316f89bfbde7d9ab23ca2e25604af290:/README#l4
  while in 'blame_incremental' view called with:
    http://git.example.com/w/git.git/blame_incremental/HEAD:/README
  we have "partial query" form
    http://git.example.com/w/git.git?;a=blame_incremental;hb=e83c5163316f89bfbde7d9ab23ca2e25604af290;f=README#l4
  Changing this would require implementing something akin to href()
  subroutine from gitweb.perl in JavaScript
* 'blame_incremental' always uses "rowspan" attribute, even if
  rowspan="1".  This is not visible to user.  (The code actually
  could work without it).

This patch adds GITWEB_BLAMEJS compile configuration option, and
modifies git-instaweb.sh to take blame.js into account, but it does not
update gitweb/README file (as it is only proof of concept patch).  The
code for git-instaweb.sh was taken from Pasky's patch.

Signed-off-by: Fredrik Kuivinen <frekui@gmail.com>
Signed-off-by: Petr Baudis <pasky@suse.cz>
Signed-off-by: Jakub Narebski <jnareb@gmail.com>
---
Refrences:
1. Original patch by Frederik Kuivinen
   http://article.gmane.org/gmane.comp.version-control.git/41361
2. Tweaked up version by Petr Baudis
   http://article.gmane.org/gmane.comp.version-control.git/47614
   http://article.gmane.org/gmane.comp.version-control.git/56657
3. New link rewriting and some optimization in Matrin Koegler
   series introducing some JavaScript support in Git
   http://thread.gmane.org/gmane.comp.version-control.git/47902/focus=47905   
4. My earlier patches
   http://thread.gmane.org/gmane.comp.version-control.git/102657/focus=102712
   http://article.gmane.org/gmane.comp.version-control.git/123202
   http://thread.gmane.org/gmane.comp.version-control.git/123957/focus=123968

Changes compared to last version (v3):
* Try yet another method (window.createrequest()) in
  createRequestObject() function.
* Rename variable holding XMLHttpRequest object from 'http' to 'xhr'
* Separate data about group of lines which are changed by the smae
  commit (which blame the same commit): srcline, resline, numlines,
  and put it in curGroup variable instead of using Commit object
  (curCommit) for that.  handleLine() function acquires 'group' as
  second parameter.
* delete no longer needed Commit properties (to be removed)
* Simplify logic and code of selecting unprocessed part of
  XMLHttpRequest responseText for processing.  nextLine global
  variable is now named nextReadPos, code now check first if there
  are any complete unprocessed lines before doing split('\n'),
  and there is now no need to remove incomplete line from 'lines'.
  This code which was inside handleResponse() can now be found in
  processData subroutine.
* Separate parts of handleResponse() as a cleanup and in preparation
  for having (simpler) event handlers for 'progress', 'load' and
  'error' W3C Progress Events, and having 'readystatechange' handler
  to be just dispatcher for those event handlers.  Introduce functions:
  processBlameLines, processData, handleError and responseLoaded
* Use DOM 2 HTML "elem.style.cssText = value;" instead of 
  DOM 2 Core "elem.setAttribute('style', value);"
* Add a few 'work in progress' comments.
* Remove comment about 'multipart/x-mixed-replace': it is
  non-standard, and it requires server to know when chunks ands to
  send replacements, something that cannot easily be done: incremental
  git-blame sends data in chunks, but gitweb doesn't know when they
  end.

TODO list:
* Use W3C Progress Events instead of 'readystatechange' event
    http://www.w3.org/TR/progress-events/
    http://www.w3.org/TR/XMLHttpRequest2/
    http://www.nczonline.net/blog/2009/07/09/firefox-35firebug-xmlhttprequest-and-readystatechange-bug/
  if XMLHttpResponse supports it, 'readystatechange' event + poll
  timer otherwise.
* handleResponse is used both as onreadystatechange and pollTimer;
  if onreadystatechange works for partial responses we can turn off
  the timer.
* Clean up handling concurrency, i.e. dealing with situation when
  handleResponse event handler is called before previous call finished
  working.  Currently it is done using inProgress flag, and busy-read
  while loop.
* Get rid of global variables, if possible.
* Instead of running startBlame, put it in window.onload handler
* Rename blame.js to gitweb.js to have all JavaScript in a single
  file.  Note that this would require changes to next commit in
  series (enabling 'blame_incremental' view if browser has javaScript
  turned on).

TODO for future commits:
* Remove (fade out) progress bar and progress info after blame
  incremental finished run (left for a separate commit).
* Profile blame.js using YUI Profiler or other JavaScript profile tool
    http://developer.yahoo.com/yui/profiler/
  to check whether performance improvements described in articles
  on NCZOnline blog by Nicholas C. Zakas are required, and would help
    http://www.nczonline.net/blog/
* Check whether it is worth to do some server processing of
  incremental blame output, and send e.g. JSON and not text/plain
  of raw 'git blame --incremental' output.
* Check how supported is 'multipart/x-mixed-replace' mimetype for data
  pushed from server (and how to correctly implement it); perhaps that
  would be a solution to concurrency problem?
* Check whether it would make sense to use some lightweight JavaScript
  library (framework) like jQuery, Prototype, ExtJS, MooTools, etc.
* Minify JavaScript during building gitweb/gitweb.cgi, if minification
  tool is found.


 Makefile           |    6 +-
 git-instaweb.sh    |    7 +
 gitweb/blame.js    |  819 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 gitweb/gitweb.css  |   16 +
 gitweb/gitweb.perl |  271 ++++++++++++------
 5 files changed, 1032 insertions(+), 87 deletions(-)
 create mode 100644 gitweb/blame.js

diff --git a/Makefile b/Makefile
index daf4296..cb93aa3 100644
--- a/Makefile
+++ b/Makefile
@@ -265,6 +265,7 @@ GITWEB_HOMETEXT = indextext.html
 GITWEB_CSS = gitweb.css
 GITWEB_LOGO = git-logo.png
 GITWEB_FAVICON = git-favicon.png
+GITWEB_BLAMEJS = blame.js
 GITWEB_SITE_HEADER =
 GITWEB_SITE_FOOTER =
 
@@ -1407,13 +1408,14 @@ gitweb/gitweb.cgi: gitweb/gitweb.perl
 	    -e 's|++GITWEB_CSS++|$(GITWEB_CSS)|g' \
 	    -e 's|++GITWEB_LOGO++|$(GITWEB_LOGO)|g' \
 	    -e 's|++GITWEB_FAVICON++|$(GITWEB_FAVICON)|g' \
+	    -e 's|++GITWEB_BLAMEJS++|$(GITWEB_BLAMEJS)|g' \
 	    -e 's|++GITWEB_SITE_HEADER++|$(GITWEB_SITE_HEADER)|g' \
 	    -e 's|++GITWEB_SITE_FOOTER++|$(GITWEB_SITE_FOOTER)|g' \
 	    $< >$@+ && \
 	chmod +x $@+ && \
 	mv $@+ $@
 
-git-instaweb: git-instaweb.sh gitweb/gitweb.cgi gitweb/gitweb.css
+git-instaweb: git-instaweb.sh gitweb/gitweb.cgi gitweb/gitweb.css gitweb/blame.js
 	$(QUIET_GEN)$(RM) $@ $@+ && \
 	sed -e '1s|#!.*/sh|#!$(SHELL_PATH_SQ)|' \
 	    -e 's/@@GIT_VERSION@@/$(GIT_VERSION)/g' \
@@ -1422,6 +1424,8 @@ git-instaweb: git-instaweb.sh gitweb/gitweb.cgi gitweb/gitweb.css
 	    -e '/@@GITWEB_CGI@@/d' \
 	    -e '/@@GITWEB_CSS@@/r gitweb/gitweb.css' \
 	    -e '/@@GITWEB_CSS@@/d' \
+	    -e '/@@GITWEB_BLAMEJS@@/r gitweb/blame.js' \
+	    -e '/@@GITWEB_BLAMEJS@@/d' \
 	    -e 's|@@PERL@@|$(PERL_PATH_SQ)|g' \
 	    $@.sh > $@+ && \
 	chmod +x $@+ && \
diff --git a/git-instaweb.sh b/git-instaweb.sh
index 5f5cac7..0288450 100755
--- a/git-instaweb.sh
+++ b/git-instaweb.sh
@@ -331,8 +331,15 @@ gitweb_css () {
 EOFGITWEB
 }
 
+gitweb_blamejs () {
+	cat > "$1" <<\EOFGITWEB
+@@GITWEB_BLAMEJS@@
+EOFGITWEB
+}
+
 gitweb_cgi "$GIT_DIR/gitweb/gitweb.cgi"
 gitweb_css "$GIT_DIR/gitweb/gitweb.css"
+gitweb_blamejs "$GIT_DIR/gitweb/blame.js"
 
 case "$httpd" in
 *lighttpd*)
diff --git a/gitweb/blame.js b/gitweb/blame.js
new file mode 100644
index 0000000..9230cb7
--- /dev/null
+++ b/gitweb/blame.js
@@ -0,0 +1,819 @@
+// Copyright (C) 2007, Fredrik Kuivinen <frekui@gmail.com>
+//               2007, Petr Baudis <pasky@suse.cz>
+//          2008-2009, Jakub Narebski <jnareb@gmail.com>
+
+/**
+ * @fileOverview JavaScript part of 'blame_incremental' action in gitweb.
+ * @license GPLv2 or later
+ */
+
+/*
+ * This code uses DOM methods instead of (nonstandard) innerHTML
+ * to modify page.
+ *
+ * innerHTML is non-standard IE extension, though supported by most
+ * browsers; however Firefox up to version 1.5 didn't implement it in
+ * a strict mode (application/xml+xhtml mimetype).  Also my simple
+ * benchmarks show that using elem.firstChild.data = 'content' is
+ * slightly faster than elem.innerHTML = 'content', if more fragile
+ * (text element fragment must exists), and less feature-rich (we
+ * cannot add HTML).
+ */
+
+/* ============================================================ */
+/* generic utility functions */
+
+var DEBUG = 0;
+function debug(str) {
+	if (DEBUG) {
+		alert(str);
+	}
+}
+
+/**
+ * pad number N with nonbreakable spaces on the left, to WIDTH characters
+ * example: spacePad(12, 3) == '&nbsp;12' ('&nbsp;' is nonbreakable space)
+ *
+ * @param {Number} n: number to pad
+ * @param {Number} width: visible width of output
+ * @returns {String} N prefixed with (WIDTH - N.length) x '&nbsp;'
+ */
+function spacePad(n, width) {
+	var prefix = '';
+
+	width -= n.toString().length;
+	while (width > 1) {
+		prefix += '&nbsp;';
+		width--;
+	}
+	return prefix + n;
+}
+
+/**
+ * Pad INPUT on the left to SIZE width, using given padding character CH,
+ * for example padLeft('a', 3, '_') is '__a'.
+ *
+ * @param {String} input: input value converted to string.
+ * @param {Number} size: desired length of output.
+ * @param {String} ch: single character to prefix to string.
+ *
+ * @returns {String} Modified string, at least SIZE length.
+ */
+function padLeft(input, size, ch) {
+	var s = input + "";
+	while (s.length < size) {
+		s = ch + s;
+	}
+	return s;
+}
+
+/**
+ * Create XMLHttpRequest object in cross-browser way
+ * @returns XMLHttpRequest object, or null
+ */
+function createRequestObject() {
+	try {
+		return new XMLHttpRequest();
+	} catch (e) {}
+	try {
+		return window.createRequest();
+	} catch (e) {}
+	try {
+		return new ActiveXObject("Msxml2.XMLHTTP");
+	} catch (e) {}
+	try {
+		return new ActiveXObject("Microsoft.XMLHTTP");
+	} catch (e) {}
+
+	//debug("XMLHttpRequest not supported");
+	return null;
+}
+
+/* ============================================================ */
+/* utility/helper functions (and variables) */
+
+var xhr;        // XMLHttpRequest object
+var projectUrl; // partial query + separator ('?' or ';')
+
+// 'commits' is an associative map. It maps SHA1s to Commit objects.
+var commits = {};
+
+/**
+ * constructor for Commit objects, used in 'blame'
+ * @class Represents a blamed commit
+ * @param {String} sha1: SHA-1 identifier of a commit
+ */
+function Commit(sha1) {
+	if (this instanceof Commit) {
+		this.sha1 = sha1;
+		this.nprevious = 0; /* number of 'previous', effective parents */
+	} else {
+		return new Commit(sha1);
+	}
+}
+
+/* ............................................................ */
+/* progress info, timing, error reporting */
+
+var blamedLines = 0;
+var totalLines  = '???';
+var div_progress_bar;
+var div_progress_info;
+
+/**
+ * Detects how many lines does a blamed file have,
+ * This information is used in progress info
+ *
+ * @returns {Number|String} Number of lines in file, or string '...'
+ */
+function countLines() {
+	var table =
+		document.getElementById('blame_table') ||
+		document.getElementsByTagName('table')[0];
+
+	if (table) {
+		return table.getElementsByTagName('tr').length - 1; // for header
+	} else {
+		return '...';
+	}
+}
+
+/**
+ * update progress info and length (width) of progress bar
+ */
+function updateProgressInfo() {
+	if (!div_progress_info) {
+		div_progress_info = document.getElementById('progress_info');
+	}
+	if (!div_progress_bar) {
+		div_progress_bar = document.getElementById('progress_bar');
+	}
+	if (!div_progress_info && !div_progress_bar) {
+		return;
+	}
+
+	var percentage = Math.floor(100.0*blamedLines/totalLines);
+
+	if (div_progress_info) {
+		div_progress_info.firstChild.data  = blamedLines + ' / ' + totalLines +
+			' (' + spacePad(percentage, 3) + '%)';
+	}
+
+	if (div_progress_bar) {
+		//div_progress_bar.setAttribute('style', 'width: '+percentage+'%;');
+		div_progress_bar.style.width = percentage + '%';
+	}
+}
+
+
+var t_interval_server = '';
+var cmds_server = '';
+var t0 = new Date();
+
+/**
+ * write how much it took to generate data, and to run script
+ */
+function writeTimeInterval() {
+	var info_time = document.getElementById('generate_time');
+	if (!info_time || !t_interval_server) {
+		return;
+	}
+	var t1 = new Date();
+	info_time.firstChild.data += ' + (' +
+		t_interval_server + 's server blame_data / ' +
+		(t1.getTime() - t0.getTime())/1000 + 's client JavaScript)';
+
+	var info_cmds = document.getElementById('generate_cmd');
+	if (!info_time || !cmds_server) {
+		return;
+	}
+	info_cmds.firstChild.data += ' + ' + cmds_server;
+}
+
+/**
+ * show an error message alert to user within page (in prohress info area)
+ * @param {String} str: plain text error message (no HTML)
+ */
+function errorInfo(str) {
+	if (!div_progress_info) {
+		div_progress_info = document.getElementById('progress_info');
+	}
+	if (div_progress_info) {
+		div_progress_info.className = 'error';
+		div_progress_info.firstChild.data = str;
+	}
+}
+
+/* ............................................................ */
+/* coloring rows during blame_data (git blame --incremental) run */
+
+/**
+ * used to extract N from 'colorN', where N is a number,
+ * @constant
+ */
+var colorRe = /\bcolor([0-9]*)\b/;
+
+/**
+ * return N if <tr class="colorN">, otherwise return null
+ * (some browsers require CSS class names to begin with letter)
+ *
+ * @param {HTMLElement} tr: table row element to check
+ * @param {String} tr.className: 'class' attribute of tr element
+ * @returns {Number|null} N if tr.className == 'colorN', otherwise null
+ */
+function getColorNo(tr) {
+	if (!tr) {
+		return null;
+	}
+	var className = tr.className;
+	if (className) {
+		var match = colorRe.exec(className);
+		if (match) {
+			return parseInt(match[1], 10);
+		}
+	}
+	return null;
+}
+
+var colorsFreq = [0, 0, 0];
+/**
+ * return one of given possible colors (curently least used one)
+ * example: chooseColorNoFrom(2, 3) returns 2 or 3
+ *
+ * @param {Number[]} arguments: one or more numbers
+ *        assumes that  1 <= arguments[i] <= colorsFreq.length
+ * @returns {Number} Least used color number from arguments
+ */
+function chooseColorNoFrom() {
+	// choose the color which is least used
+	var colorNo = arguments[0];
+	for (var i = 1; i < arguments.length; i++) {
+		if (colorsFreq[arguments[i]-1] < colorsFreq[colorNo-1]) {
+			colorNo = arguments[i];
+		}
+	}
+	colorsFreq[colorNo-1]++;
+	return colorNo;
+}
+
+/**
+ * given two neigbour <tr> elements, find color which would be different
+ * from color of both of neighbours; used to 3-color blame table
+ *
+ * @param {HTMLElement} tr_prev
+ * @param {HTMLElement} tr_next
+ * @returns {Number} color number N such that
+ * colorN != tr_prev.className && colorN != tr_next.className
+ */
+function findColorNo(tr_prev, tr_next) {
+	var color_prev = getColorNo(tr_prev);
+	var color_next = getColorNo(tr_next);
+
+
+	// neither of neighbours has color set
+	// THEN we can use any of 3 possible colors
+	if (!color_prev && !color_next) {
+		return chooseColorNoFrom(1,2,3);
+	}
+
+	// either both neighbours have the same color,
+	// or only one of neighbours have color set
+	// THEN we can use any color except given
+	var color;
+	if (color_prev === color_next) {
+		color = color_prev; // = color_next;
+	} else if (!color_prev) {
+		color = color_next;
+	} else if (!color_next) {
+		color = color_prev;
+	}
+	if (color) {
+		return chooseColorNoFrom((color % 3) + 1, ((color+1) % 3) + 1);
+	}
+
+	// neighbours have different colors
+	// THEN there is only one color left
+	return (3 - ((color_prev + color_next) % 3));
+}
+
+/* ............................................................ */
+/* coloring rows like 'blame' after 'blame_data' finishes */
+
+/**
+ * returns true if given row element (tr) is first in commit group
+ * to be used only after 'blame_data' finishes (after processing)
+ *
+ * @param {HTMLElement} tr: table row
+ * @returns {Boolean} true if TR is first in commit group
+ */
+function isStartOfGroup(tr) {
+	return tr.firstChild.className === 'sha1';
+}
+
+/**
+ * change colors to use zebra coloring (2 colors) instead of 3 colors
+ * concatenate neighbour commit groups belonging to the same commit
+ */
+function fixColorsAndGroups() {
+	var colorClasses = ['light', 'dark'];
+	var linenum = 1;
+	var tr, prev_group;
+	var colorClass = 0;
+	var table =
+		document.getElementById('blame_table') ||
+		document.getElementsByTagName('table')[0];
+
+	while ((tr = document.getElementById('l'+linenum))) {
+	// index origin is 0, which is table header; start from 1
+	//while ((tr = table.rows[linenum])) { // <- it is slower
+		if (isStartOfGroup(tr, linenum, document)) {
+			if (prev_group &&
+			    prev_group.firstChild.firstChild.href ===
+			            tr.firstChild.firstChild.href) {
+				// we have to concatenate groups
+				var prev_rows = prev_group.firstChild.rowSpan || 1;
+				var curr_rows =         tr.firstChild.rowSpan || 1;
+				prev_group.firstChild.rowSpan = prev_rows + curr_rows;
+				//tr.removeChild(tr.firstChild);
+				tr.deleteCell(0); // DOM2 HTML way
+			} else {
+				colorClass = (colorClass + 1) % 2;
+				prev_group = tr;
+			}
+		}
+		var tr_class = tr.className;
+		tr.className = tr_class.replace(colorRe, colorClasses[colorClass]);
+		linenum++;
+	}
+}
+
+/* ............................................................ */
+/* time and data */
+
+/**
+ * used to extract hours and minutes from timezone info, e.g '-0900'
+ * @constant
+ */
+var tzRe = /^([+-][0-9][0-9])([0-9][0-9])$/;
+
+/**
+ * return date in local time formatted in iso-8601 like format
+ * 'yyyy-mm-dd HH:MM:SS +/-ZZZZ' e.g. '2005-08-07 21:49:46 +0200'
+ *
+ * @param {Number} epoch: seconds since '00:00:00 1970-01-01 UTC'
+ * @param {String} timezoneInfo: numeric timezone '(+|-)HHMM'
+ * @returns {String} date in local time in iso-8601 like format
+ */
+function formatDateISOLocal(epoch, timezoneInfo) {
+	var match = tzRe.exec(timezoneInfo);
+	// date corrected by timezone
+	var localDate = new Date(1000 * (epoch +
+		(parseInt(match[1],10)*3600 + parseInt(match[2],10)*60)));
+	var localDateStr = // e.g. '2005-08-07'
+		localDate.getUTCFullYear()                 + '-' +
+		padLeft(localDate.getUTCMonth()+1, 2, '0') + '-' +
+		padLeft(localDate.getUTCDate(),    2, '0');
+	var localTimeStr = // e.g. '21:49:46'
+		padLeft(localDate.getUTCHours(),   2, '0') + ':' +
+		padLeft(localDate.getUTCMinutes(), 2, '0') + ':' +
+		padLeft(localDate.getUTCSeconds(), 2, '0');
+
+	return localDateStr + ' ' + localTimeStr + ' ' + timezoneInfo;
+}
+
+/* ............................................................ */
+/* unquoting/unescaping filenames */
+
+/**
+ * Used to detect escape sequences (octal e.g. \008 and symbolic e.g. \n)
+ * @constant
+ */
+var escCodeRe = /\\([^0-7]|[0-7]{1,3})/g;
+
+/**
+ * unquote maybe git-quoted filename
+ * e.g. 'aa' -> 'aa', '"a\ta"' -> 'a	a'
+ *
+ * @param {String} str: git-quoted string
+ * @returns {String} Unquoted and unescaped string
+ */
+function unquote(str) {
+	function unq(seq) {
+		var es = { // character escape codes, aka escape sequences
+			t: "\t",   // tab            (HT, TAB)
+			n: "\n",   // newline        (NL)
+			r: "\r",   // return         (CR)
+			f: "\f",   // form feed      (FF)
+			b: "\b",   // backspace      (BS)
+			a: "\x07", // alarm (bell)   (BEL)
+			e: "\x1B", // escape         (ESC)
+			v: "\v"    // vertical tab   (VT)
+		};
+
+		if (seq.search(/^[0-7]{1,3}$/) !== -1) {
+			// octal char sequence
+			return String.fromCharCode(parseInt(seq, 8));
+		} else if (seq in es) {
+			// C escape sequence, aka character escape code
+			return es[seq];
+		}
+		// quoted ordinary character
+		return seq;
+	}
+
+	var match = str.match(/^\"(.*)\"$/);
+	if (match) {
+		str = match[1];
+		// perhaps str = eval('"'+str+'"'); would be enough?
+		str = str.replace(escCodeRe,
+			function (substr, p1, offset, s) { return unq(p1); });
+	}
+	return str;
+}
+
+/* ============================================================ */
+/* main part: parsing response */
+
+/**
+ * Function called for each blame entry, as soon as it finishes.
+ * It updates page via DOM manipulation, adding sha1 info, etc.
+ *
+ * @param {Commit} commit: blamed commit
+ * @param {Object} group: object representing group of lines,
+ *                        which blame the same commit (blame entry)
+ */
+function handleLine(commit, group) {
+	/* 
+	   This is the structure of the HTML fragment we are working
+	   with:
+
+	   <tr id="l123" class="">
+	     <td class="sha1" title=""><a href=""> </a></td>
+	     <td class="linenr"><a class="linenr" href="">123</a></td>
+	     <td class="pre"># times (my ext3 doesn&#39;t).</td>
+	   </tr>
+	*/
+
+	var resline = group.resline;
+
+	// format date and time string only once per commit
+	if (!commit.info) {
+		/* e.g. 'Kay Sievers, 2005-08-07 21:49:46 +0200' */
+		commit.info = commit.author + ', ' +
+			formatDateISOLocal(commit.authorTime, commit.authorTimezone);
+		// delete properties no longer needed, to reduce memory footprint
+		//delete commit.author;
+		delete commit.authorTime;
+		delete commit.authorTimezone;
+	}
+
+	// color depends on group of lines, not only on blamed commit
+	var colorNo = findColorNo(
+		document.getElementById('l'+(resline-1)),
+		document.getElementById('l'+(resline+group.numlines))
+	);
+
+	// loop over lines in commit group
+	for (var i = 0; i < group.numlines; i++, resline++) {
+		var tr = document.getElementById('l'+resline);
+		if (!tr) {
+			//debug('tr is null! resline: ' + resline);
+			break;
+		}
+		/*
+			<tr id="l123" class="">
+			  <td class="sha1" title=""><a href=""> </a></td>
+			  <td class="linenr"><a class="linenr" href="">123</a></td>
+			  <td class="pre"># times (my ext3 doesn&#39;t).</td>
+			</tr>
+		*/
+		var td_sha1  = tr.firstChild;
+		var a_sha1   = td_sha1.firstChild;
+		var a_linenr = td_sha1.nextSibling.firstChild;
+
+		/* <tr id="l123" class=""> */
+		var tr_class = '';
+		if (colorNo !== null) {
+			tr_class = 'color'+colorNo;
+		}
+		if (commit.boundary) {
+			tr_class += ' boundary';
+		}
+		if (commit.nprevious === 0) {
+			tr_class += ' no-previous';
+		} else if (commit.nprevious > 1) {
+			tr_class += ' multiple-previous';
+		}
+		tr.className = tr_class;
+
+		/* <td class="sha1" title="?" rowspan="?"><a href="?">?</a></td> */
+		if (i === 0) {
+			td_sha1.title = commit.info;
+			td_sha1.rowSpan = group.numlines;
+
+			a_sha1.href = projectUrl + 'a=commit;h=' + commit.sha1;
+			a_sha1.firstChild.data = commit.sha1.substr(0, 8);
+			if (group.numlines >= 2) {
+				var fragment = document.createDocumentFragment();
+				var br   = document.createElement("br");
+				var text = document.createTextNode(
+					commit.author.match(/\b([A-Z])\B/g).join(''));
+				if (br && text) {
+					var elem = fragment || td_sha1;
+					elem.appendChild(br);
+					elem.appendChild(text);
+					if (fragment) {
+						td_sha1.appendChild(fragment);
+					}
+				}
+			}
+		} else {
+			//tr.removeChild(td_sha1); // DOM2 Core way
+			tr.deleteCell(0); // DOM2 HTML way
+		}
+
+		/* <td class="linenr"><a class="linenr" href="?">123</a></td> */
+		var linenr_commit =
+			('previous' in commit ? commit.previous : commit.sha1);
+		var linenr_filename =
+			('file_parent' in commit ? commit.file_parent : commit.filename);
+		a_linenr.href = projectUrl + 'a=blame_incremental' +
+			';hb=' + linenr_commit +
+			';f='  + encodeURIComponent(linenr_filename) +
+			'#l' + (group.srcline + i);
+
+		blamedLines++;
+
+		//updateProgressInfo();
+	}
+}
+
+// ----------------------------------------------------------------------
+
+var prevDataLength = -1;  // used to detect if we have new data
+var nextReadPos = 0;      // where unread part of response starts
+var inProgress = false;   // are we processing response
+
+/**#@+
+ * @constant
+ */
+var sha1Re = /^([0-9a-f]{40}) ([0-9]+) ([0-9]+) ([0-9]+)/;
+var infoRe = /^([a-z-]+) ?(.*)/;
+var endRe  = /^END ?([^ ]*) ?(.*)/;
+/**@-*/
+
+var curCommit = new Commit();
+var curGroup  = {};
+
+var pollTimer = null;
+
+/*
+ * W3C Progress Events (http://www.w3.org/TR/progress-events)
+ * events: loadstart, progress, error, abort, load
+ * interface: lengthComputable, loaded, total (0 if unknown)
+ */
+
+/*
+ * handleResponse ->
+ *   handleError (or onXHReqError, onError, ...)
+ *   handleAbort (?)
+ *   handleProgress
+ *     parseResponse / parseProgress
+ *       parseBlame | parseJSON
+ *         handleLine
+ *         updateProgressInfo
+ *   handleLoad
+ */
+
+/**
+ * Parse output from 'git blame --incremental [...]', received via
+ * XMLHttpRequest from server (blamedataUrl), and call handleLine
+ * (which updates page) as soon as blame entry is completed.
+ *
+ * @param {String[]} lines: new complete lines from blamedata server
+ */
+function processBlameLines(lines) {
+	var match;
+
+	for (var i = 0, len = lines.length; i < len; i++) {
+
+		if ((match = sha1Re.exec(lines[i]))) {
+			var sha1 = match[1];
+			var srcline  = parseInt(match[2], 10);
+			var resline  = parseInt(match[3], 10);
+			var numlines = parseInt(match[4], 10);
+
+			var c = commits[sha1];
+			if (!c) {
+				c = new Commit(sha1);
+				commits[sha1] = c;
+			}
+			curCommit = c;
+
+			curGroup.srcline = srcline;
+			curGroup.resline = resline;
+			curGroup.numlines = numlines;
+
+		} else if ((match = infoRe.exec(lines[i]))) {
+			var info = match[1];
+			var data = match[2];
+			switch (info) {
+			case 'filename':
+				curCommit.filename = unquote(data);
+				// 'filename' information terminates the entry
+				handleLine(curCommit, curGroup);
+				updateProgressInfo();
+				break;
+			case 'author':
+				curCommit.author = data;
+				break;
+			case 'author-time':
+				curCommit.authorTime = parseInt(data, 10);
+				break;
+			case 'author-tz':
+				curCommit.authorTimezone = data;
+				break;
+			case 'previous':
+				curCommit.nprevious++;
+				// store only first 'previous' header
+				if (!'previous' in curCommit) {
+					var parts = data.split(' ', 2);
+					curCommit.previous    = parts[0];
+					curCommit.file_parent = unquote(parts[1]);
+				}
+				break;
+			case 'boundary':
+				//debug('Boundary commit: '+curCommit.sha1);
+				curCommit.boundary = true;
+				break;
+			} // end switch
+
+		} else if ((match = endRe.exec(lines[i]))) {
+			t_interval_server = match[1];
+			cmds_server = match[2];
+			//debug('END: '+lines[i]);
+
+		} else if (lines[i] !== '') {
+			//debug('malformed line: ' + lines[i]);
+
+		} // end if (match)
+
+	} // end for (lines)
+}
+
+/**
+ * Process new data and return pointer to end of processed part
+ *
+ * @param {String} unprocessed: new data (from nextReadPos)
+ * @param {Number} nextReadPos: end of last processed data
+ * @return {Number} end of processed data (new value for nextReadPos)
+ */
+function processData(unprocessed, nextReadPos) {
+	var lastLineEnd = unprocessed.lastIndexOf('\n');
+	if (lastLineEnd !== -1) {
+		var lines = unprocessed.substring(0, lastLineEnd).split('\n');
+		nextReadPos += lastLineEnd + 1 /* 1 == '\n'.length */;
+
+		processBlameLines(lines);
+	} // end if
+
+	return nextReadPos;
+}
+
+/**
+ * Handle XMLHttpRequest errors
+ */
+function handleError() {
+	errorInfo('Server error: ' +
+		xhr.status + ' - ' + (xhr.statusText || 'Error contacting server'));
+
+	clearInterval(pollTimer);
+	commits = {}; // free memory
+
+	inProgress = false;
+}
+
+/**
+ * Called after XMLHttpRequest finishes (loads)
+ */
+function responseLoaded() {
+	clearInterval(pollTimer);
+
+	fixColorsAndGroups();
+	writeTimeInterval();
+	commits = {}; // free memory
+
+	inProgress = false;
+}
+
+/**
+ * handler for XMLHttpRequest onreadystatechange event
+ * @see startBlame
+ */
+function handleResponse() {
+	//debug('handleResp ready: ' + xhr.readyState +
+	//      ' respText null?: ' + (xhr.responseText === null) +
+	//      ' progress: ' + inProgress);
+
+	/*
+	 * xhr.readyState
+	 *
+	 *  Value  Constant (W3C)    Description
+	 *  -------------------------------------------------------------------
+	 *  0      UNSENT            open() has not been called yet.
+	 *  1      OPENED            send() has not been called yet.
+	 *  2      HEADERS_RECEIVED  send() has been called, and headers
+	 *                           and status are available.
+	 *  3      LOADING           Downloading; responseText holds partial data.
+	 *  4      DONE              The operation is complete.
+	 */
+
+	if (xhr.readyState !== 4 && xhr.readyState !== 3) {
+		return;
+	}
+
+	// the server returned error
+	if (xhr.readyState === 3 && xhr.status !== 200) {
+		return;
+	}
+	if (xhr.readyState === 4 && xhr.status !== 200) {
+		handleError();
+		return;
+	}
+
+	// In konqueror xhr.responseText is sometimes null here...
+	if (xhr.responseText === null) {
+		return;
+	}
+
+	// in case we were called before finished processing
+	if (inProgress) {
+		return;
+	} else {
+		inProgress = true;
+	}
+
+	// extract new whole (complete) lines, and process them
+	while (prevDataLength !== xhr.responseText.length) {
+		if (xhr.readyState === 4 &&
+		    prevDataLength === xhr.responseText.length) {
+			break;
+		}
+
+		prevDataLength = xhr.responseText.length;
+		var unprocessed = xhr.responseText.substring(nextReadPos);
+		nextReadPos = processData(unprocessed, nextReadPos);
+	} // end while
+
+	// did we finish work?
+	if (xhr.readyState === 4 &&
+	    prevDataLength === xhr.responseText.length) {
+		responseLoaded();
+	}
+
+	inProgress = false;
+}
+
+// ============================================================
+// ------------------------------------------------------------
+
+/**
+ * Incrementally update line data in blame_incremental view in gitweb.
+ *
+ * @param {String} blamedataUrl: URL to server script generating blame data.
+ * @param {String} bUrl: partial URL to project, used to generate links.
+ *
+ * Called from 'blame_incremental' view after loading table with
+ * file contents, a base for blame view.
+*/
+function startBlame(blamedataUrl, bUrl) {
+	//debug('startBlame('+blamedataUrl+', '+bUrl+')');
+
+	xhr = createRequestObject();
+	if (!xhr) {
+		errorInfo('ERROR: XMLHttpRequest not supported');
+		return;
+	}
+
+	t0 = new Date();
+	projectUrl = bUrl + (bUrl.indexOf('?') === -1 ? '?' : ';');
+	if ((div_progress_bar = document.getElementById('progress_bar'))) {
+		//div_progress_bar.setAttribute('style', 'width: 100%;');
+		div_progress_bar.style.cssText = 'width: 100%;';
+	}
+	totalLines = countLines();
+	updateProgressInfo();
+
+	xhr.open('get', blamedataUrl);
+	xhr.setRequestHeader('Accept', 'text/plain');
+	xhr.onreadystatechange = handleResponse;
+	//xhr.onreadystatechange = function () { handleResponse(xhr); };
+	xhr.send(null);
+
+	// not all browsers call onreadystatechange event on each server flush
+	if (!DEBUG) {
+		pollTimer = setInterval(handleResponse, 1000);
+	}
+}
+
+// end of blame.js
diff --git a/gitweb/gitweb.css b/gitweb/gitweb.css
index 8f68fe3..c9a7501 100644
--- a/gitweb/gitweb.css
+++ b/gitweb/gitweb.css
@@ -250,6 +250,11 @@ tr.no-previous td.linenr {
 	font-weight: bold;
 }
 
+/* for 'blame_incremental', during processing */
+tr.color1 { background-color: #f6fff6; }
+tr.color2 { background-color: #f6f6ff; }
+tr.color3 { background-color: #fff6f6; }
+
 td {
 	padding: 2px 5px;
 	font-size: 100%;
@@ -341,6 +346,17 @@ td.mode {
 	font-family: monospace;
 }
 
+/* progress of blame_interactive */
+div#progress_bar {
+	height: 2px;
+	margin-bottom: -2px;
+	background-color: #d8d9d0;
+}
+div#progress_info {
+	float: right;
+	text-align: right;
+}
+
 /* styling of diffs (patchsets): commitdiff and blobdiff views */
 div.diff.header,
 div.diff.extended_header {
diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index 6f47659..cf1b8bb 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -96,6 +96,8 @@ our $stylesheet = undef;
 our $logo = "++GITWEB_LOGO++";
 # URI of GIT favicon, assumed to be image/png type
 our $favicon = "++GITWEB_FAVICON++";
+# URI of blame.js
+our $blamejs = "++GITWEB_BLAMEJS++";
 
 # URI and label (title) of GIT logo link
 #our $logo_url = "http://www.kernel.org/pub/software/scm/git/docs/";
@@ -564,6 +566,8 @@ our %cgi_param_mapping = @cgi_param_mapping;
 # we will also need to know the possible actions, for validation
 our %actions = (
 	"blame" => \&git_blame,
+	"blame_incremental" => \&git_blame_incremental,
+	"blame_data" => \&git_blame_data,
 	"blobdiff" => \&git_blobdiff,
 	"blobdiff_plain" => \&git_blobdiff_plain,
 	"blob" => \&git_blob,
@@ -4789,7 +4793,9 @@ sub git_tag {
 	git_footer_html();
 }
 
-sub git_blame {
+sub git_blame_common {
+	my $format = shift || 'porcelain';
+
 	# permissions
 	gitweb_check_feature('blame')
 		or die_error(403, "Blame view not allowed");
@@ -4811,10 +4817,43 @@ sub git_blame {
 		}
 	}
 
-	# run git-blame --porcelain
-	open my $fd, "-|", git_cmd(), "blame", '-p',
-		$hash_base, '--', $file_name
-		or die_error(500, "Open git-blame failed");
+	my $fd;
+	if ($format eq 'incremental') {
+		# get file contents (as base)
+		open $fd, "-|", git_cmd(), 'cat-file', 'blob', $hash
+			or die_error(500, "Open git-cat-file failed");
+	} elsif ($format eq 'data') {
+		# run git-blame --incremental
+		open $fd, "-|", git_cmd(), "blame", "--incremental",
+			$hash_base, "--", $file_name
+			or die_error(500, "Open git-blame --incremental failed");
+	} else {
+		# run git-blame --porcelain
+		open $fd, "-|", git_cmd(), "blame", '-p',
+			$hash_base, '--', $file_name
+			or die_error(500, "Open git-blame --porcelain failed");
+	}
+
+	# incremental blame data returns early
+	if ($format eq 'data') {
+		print $cgi->header(
+			-type=>"text/plain", -charset => "utf-8",
+			-status=> "200 OK");
+		local $| = 1; # output autoflush
+		print while <$fd>;
+		close $fd
+			or print "ERROR $!\n";
+
+		print 'END';
+		if (defined $t0 && gitweb_check_feature('timed')) {
+			print ' '.
+			      Time::HiRes::tv_interval($t0, [Time::HiRes::gettimeofday()]).
+			      ' '.$number_of_git_cmds;
+		}
+		print "\n";
+
+		return;
+	}
 
 	# page header
 	git_header_html();
@@ -4825,109 +4864,169 @@ sub git_blame {
 		$cgi->a({-href => href(action=>"history", -replay=>1)},
 		        "history") .
 		" | " .
-		$cgi->a({-href => href(action=>"blame", file_name=>$file_name)},
+		$cgi->a({-href => href(action=>$action, file_name=>$file_name)},
 		        "HEAD");
 	git_print_page_nav('','', $hash_base,$co{'tree'},$hash_base, $formats_nav);
 	git_print_header_div('commit', esc_html($co{'title'}), $hash_base);
 	git_print_page_path($file_name, $ftype, $hash_base);
 
 	# page body
+	if ($format eq 'incremental') {
+		print "<noscript>\n<div class=\"error\"><center><b>\n".
+		      "This page requires JavaScript to run.\n Use ".
+		      $cgi->a({-href => href(action=>'blame',-replay=>1)}, 'this page').
+		      " instead.\n".
+		      "</b></center></div>\n</noscript>\n";
+
+		print qq!<div id="progress_bar" style="width: 100%; background-color: yellow"></div>\n!;
+	}
+
+	print qq!<div class="page_body">\n!;
+	print qq!<div id="progress_info">... / ...</div>\n!
+		if ($format eq 'incremental');
+	print qq!<table id="blame_table" class="blame" width="100%">\n!.
+	      #qq!<col width="5.5em" /><col width="2.5em" /><col width="*" />\n!.
+	      qq!<thead>\n!.
+	      qq!<tr><th>Commit</th><th>Line</th><th>Data</th></tr>\n!.
+	      qq!</thead>\n!.
+	      qq!<tbody>\n!;
+
 	my @rev_color = qw(light dark);
 	my $num_colors = scalar(@rev_color);
 	my $current_color = 0;
-	my %metainfo = ();
 
-	print <<HTML;
-<div class="page_body">
-<table class="blame">
-<tr><th>Commit</th><th>Line</th><th>Data</th></tr>
-HTML
- LINE:
-	while (my $line = <$fd>) {
-		chomp $line;
-		# the header: <SHA-1> <src lineno> <dst lineno> [<lines in group>]
-		# no <lines in group> for subsequent lines in group of lines
-		my ($full_rev, $orig_lineno, $lineno, $group_size) =
-		   ($line =~ /^([0-9a-f]{40}) (\d+) (\d+)(?: (\d+))?$/);
-		if (!exists $metainfo{$full_rev}) {
-			$metainfo{$full_rev} = { 'nprevious' => 0 };
-		}
-		my $meta = $metainfo{$full_rev};
-		my $data;
-		while ($data = <$fd>) {
-			chomp $data;
-			last if ($data =~ s/^\t//); # contents of line
-			if ($data =~ /^(\S+)(?: (.*))?$/) {
-				$meta->{$1} = $2 unless exists $meta->{$1};
+	if ($format eq 'incremental') {
+		my $color_class = $rev_color[$current_color];
+
+		#contents of a file
+		my $linenr = 0;
+	LINE:
+		while (my $line = <$fd>) {
+			chomp $line;
+			$linenr++;
+
+			print qq!<tr id="l$linenr" class="$color_class">!.
+			      qq!<td class="sha1"><a href=""> </a></td>!.
+			      qq!<td class="linenr">!.
+			      qq!<a class="linenr" href="">$linenr</a></td>!;
+			print qq!<td class="pre">! . esc_html($line) . "</td>\n";
+			print qq!</tr>\n!;
+		}
+
+	} else { # porcelain, i.e. ordinary blame
+		my %metainfo = (); # saves information about commits
+
+		# blame data
+	LINE:
+		while (my $line = <$fd>) {
+			chomp $line;
+			# the header: <SHA-1> <src lineno> <dst lineno> [<lines in group>]
+			# no <lines in group> for subsequent lines in group of lines
+			my ($full_rev, $orig_lineno, $lineno, $group_size) =
+			   ($line =~ /^([0-9a-f]{40}) (\d+) (\d+)(?: (\d+))?$/);
+			if (!exists $metainfo{$full_rev}) {
+				$metainfo{$full_rev} = { 'nprevious' => 0 };
 			}
-			if ($data =~ /^previous /) {
-				$meta->{'nprevious'}++;
+			my $meta = $metainfo{$full_rev};
+			my $data;
+			while ($data = <$fd>) {
+				chomp $data;
+				last if ($data =~ s/^\t//); # contents of line
+				if ($data =~ /^(\S+)(?: (.*))?$/) {
+					$meta->{$1} = $2 unless exists $meta->{$1};
+				}
+				if ($data =~ /^previous /) {
+					$meta->{'nprevious'}++;
+				}
 			}
-		}
-		my $short_rev = substr($full_rev, 0, 8);
-		my $author = $meta->{'author'};
-		my %date =
-			parse_date($meta->{'author-time'}, $meta->{'author-tz'});
-		my $date = $date{'iso-tz'};
-		if ($group_size) {
-			$current_color = ($current_color + 1) % $num_colors;
-		}
-		my $tr_class = $rev_color[$current_color];
-		$tr_class .= ' boundary' if (exists $meta->{'boundary'});
-		$tr_class .= ' no-previous' if ($meta->{'nprevious'} == 0);
-		$tr_class .= ' multiple-previous' if ($meta->{'nprevious'} > 1);
-		print "<tr id=\"l$lineno\" class=\"$tr_class\">\n";
-		if ($group_size) {
-			print "<td class=\"sha1\"";
-			print " title=\"". esc_html($author) . ", $date\"";
-			print " rowspan=\"$group_size\"" if ($group_size > 1);
-			print ">";
-			print $cgi->a({-href => href(action=>"commit",
-			                             hash=>$full_rev,
-			                             file_name=>$file_name)},
-			              esc_html($short_rev));
-			if ($group_size >= 2) {
-				my @author_initials = ($author =~ /\b([[:upper:]])\B/g);
-				if (@author_initials) {
-					print "<br />" .
-					      esc_html(join('', @author_initials));
-					#           or join('.', ...)
+			my $short_rev = substr($full_rev, 0, 8);
+			my $author = $meta->{'author'};
+			my %date =
+				parse_date($meta->{'author-time'}, $meta->{'author-tz'});
+			my $date = $date{'iso-tz'};
+			if ($group_size) {
+				$current_color = ($current_color + 1) % $num_colors;
+			}
+			my $tr_class = $rev_color[$current_color];
+			$tr_class .= ' boundary' if (exists $meta->{'boundary'});
+			$tr_class .= ' no-previous' if ($meta->{'nprevious'} == 0);
+			$tr_class .= ' multiple-previous' if ($meta->{'nprevious'} > 1);
+			print "<tr id=\"l$lineno\" class=\"$tr_class\">\n";
+			if ($group_size) {
+				print "<td class=\"sha1\"";
+				print " title=\"". esc_html($author) . ", $date\"";
+				print " rowspan=\"$group_size\"" if ($group_size > 1);
+				print ">";
+				print $cgi->a({-href => href(action=>"commit",
+				                             hash=>$full_rev,
+				                             file_name=>$file_name)},
+				              esc_html($short_rev));
+				if ($group_size >= 2) {
+					my @author_initials = ($author =~ /\b([[:upper:]])\B/g);
+					if (@author_initials) {
+						print "<br />" .
+						      esc_html(join('', @author_initials));
+						#           or join('.', ...)
+					}
 				}
+				print "</td>\n";
 			}
-			print "</td>\n";
-		}
-		# 'previous' <sha1 of parent commit> <filename at commit>
-		if (exists $meta->{'previous'} &&
-		    $meta->{'previous'} =~ /^([a-fA-F0-9]{40}) (.*)$/) {
-			$meta->{'parent'} = $1;
-			$meta->{'file_parent'} = unquote($2);
-		}
-		my $linenr_commit =
-			exists($meta->{'parent'}) ?
-			$meta->{'parent'} : $full_rev;
-		my $linenr_filename =
-			exists($meta->{'file_parent'}) ?
-			$meta->{'file_parent'} : unquote($meta->{'filename'});
-		my $blamed = href(action => 'blame',
-		                  file_name => $linenr_filename,
-		                  hash_base => $linenr_commit);
-		print "<td class=\"linenr\">";
-		print $cgi->a({ -href => "$blamed#l$orig_lineno",
-		                -class => "linenr" },
-		              esc_html($lineno));
-		print "</td>";
-		print "<td class=\"pre\">" . esc_html($data) . "</td>\n";
-		print "</tr>\n";
+			# 'previous' <sha1 of parent commit> <filename at commit>
+			if (exists $meta->{'previous'} &&
+			    $meta->{'previous'} =~ /^([a-fA-F0-9]{40}) (.*)$/) {
+				$meta->{'parent'} = $1;
+				$meta->{'file_parent'} = unquote($2);
+			}
+			my $linenr_commit =
+				exists($meta->{'parent'}) ?
+				$meta->{'parent'} : $full_rev;
+			my $linenr_filename =
+				exists($meta->{'file_parent'}) ?
+				$meta->{'file_parent'} : unquote($meta->{'filename'});
+			my $blamed = href(action => 'blame',
+			                  file_name => $linenr_filename,
+			                  hash_base => $linenr_commit);
+			print "<td class=\"linenr\">";
+			print $cgi->a({ -href => "$blamed#l$orig_lineno",
+			                -class => "linenr" },
+			              esc_html($lineno));
+			print "</td>";
+			print "<td class=\"pre\">" . esc_html($data) . "</td>\n";
+			print "</tr>\n";
+		} # end while
+
 	}
-	print "</table>\n";
-	print "</div>";
+
+	# footer
+	print "</tbody>\n".
+	      "</table>\n"; # class="blame"
+	print "</div>\n";   # class="blame_body"
 	close $fd
 		or print "Reading blob failed\n";
 
-	# page footer
+	if ($format eq 'incremental') {
+		print qq!<script type="text/javascript" src="$blamejs"></script>\n!.
+		      qq!<script type="text/javascript">\n!.
+		      qq!startBlame("!. href(action=>"blame_data", -replay=>1) .qq!",\n!.
+		      qq!           "!. href() .qq!");\n!.
+		      qq!</script>\n!;
+	}
+
 	git_footer_html();
 }
 
+sub git_blame {
+	git_blame_common();
+}
+
+sub git_blame_incremental {
+	git_blame_common('incremental');
+}
+
+sub git_blame_data {
+	git_blame_common('data');
+}
+
 sub git_tags {
 	my $head = git_get_head_hash($project);
 	git_header_html();
-- 
1.6.3.3