[PATCH v3] Configurable hyperlinking in gitk

[Jeff Epler <jepler@unpythonic.net>]

Many projects use project-specific notations in changelogs to refer
to bug trackers and the like.  One example is the "Closes: #12345"
notation used in Debian.

Make gitk configurable so that arbitrary strings can be turned into
clickable links that are opened in a web browser.

Signed-off-by: Jeff Epler <jepler@unpythonic.net>
---
Since the previous patch, I
 * Renamed configuration variables to get rid of the "gitk" prefix
   to encourage other git-related programs to adopt the same
   functionality.

 * Renamed configuration variables from cryptic ".re", ".sub" to less
   cryptic ".regexp" and "subst"

 * Changed the example RE to be an ERE (no \d or \M)

 * Documented that these are POSIX EREs; hopefully that's OK.  I see
   in CodingGuidelines that in git itself "a subset of BREs" are used,
   so maybe even this is too much power.  And hopefully tcl's
   re_syntax really is close enough to an ERE superset that this isn't
   a terrible lie about the initial implementation either.

 * Added a Signed-Off-By, since I've had a number of positive feedbacks
   and the only problems I've heard of (since patch v2) are the ones
   related to 'eval' in git-web--browse.

In v2 of the patch, I had fixed a problem with %-signs in URLs and
changed the documentation example.

 Documentation/config.txt |   30 +++++++++++++++++-
 gitk-git/gitk            |   75 +++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 102 insertions(+), 3 deletions(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index ae9913b..ffc9ccf 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1064,6 +1064,10 @@ All gitcvs variables except for 'gitcvs.usecrlfattr' and
 is one of "ext" and "pserver") to make them apply only for the given
 access method.
 
+gitk.browser::
+	Specify the browser that will be used to open links generated by
+	'linkify' configuration options.
+
 grep.lineNumber::
 	If set to true, enable '-n' option by default.
 
@@ -1317,6 +1321,28 @@ interactive.singlekey::
 	setting is silently ignored if portable keystroke input
 	is not available.
 
+linkify.<name>.regexp::
+	Specify a regular expression in the POSIX Extended Regular Expression
+	syntax defining a class of strings to automatically convert to
+	hyperlinks.  This regular expression many not span multiple lines.
+	You must also specify 'linkify.<name>.subst'.
+
+linkify.<name>.subst::
+	Specify a substitution that results in the target URL for the
+	related regular expression.  Back-references like '\1' refer
+	to capturing groups in the associated regular expression.
+	You must also specify 'linkify.<name>.regexp'.
++
+For example, to automatically link from Debian-style "Closes: #nnnn"
+message to the Debian BTS,
++
+--------
+    git config linkify.debian-bts.regexp '#([1-9][0-9]*)'
+    git config linkify.debian-bts.subst 'http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=\1'
+--------
++
+Currently, only linkgit:gitk[1] converts strings to links in this fashion.
+
 log.abbrevCommit::
 	If true, makes linkgit:git-log[1], linkgit:git-show[1], and
 	linkgit:git-whatchanged[1] assume `\--abbrev-commit`. You may
@@ -1870,5 +1896,5 @@ user.signingkey::
 
 web.browser::
 	Specify a web browser that may be used by some commands.
-	Currently only linkgit:git-instaweb[1] and linkgit:git-help[1]
-	may use it.
+	Currently only linkgit:git-instaweb[1], linkgit:gitk[1],
+	and linkgit:git-help[1] may use it.
diff --git a/gitk-git/gitk b/gitk-git/gitk
index 4cde0c4..9db5525 100755
--- a/gitk-git/gitk
+++ b/gitk-git/gitk
@@ -6684,7 +6684,7 @@ proc commit_descriptor {p} {
 # append some text to the ctext widget, and make any SHA1 ID
 # that we know about be a clickable link.
 proc appendwithlinks {text tags} {
-    global ctext linknum curview
+    global ctext linknum curview linkmakers
 
     set start [$ctext index "end - 1c"]
     $ctext insert end $text $tags
@@ -6699,6 +6699,30 @@ proc appendwithlinks {text tags} {
 	setlink $linkid link$linknum
 	incr linknum
     }
+
+    if {$linkmakers == {}} return
+
+    set link_re {}
+    foreach {re rep} $linkmakers { lappend link_re $re }
+    set link_re "([join $link_re {)|(}])"
+
+    set ee 0
+    while {[regexp -indices -start $ee -- $link_re $text l]} {
+	set s [lindex $l 0]
+	set e [lindex $l 1]
+	set linktext [string range $text $s $e]
+	incr e
+	set ee $e
+
+	foreach {re rep} $linkmakers {
+	    if {![regsub $re $linktext $rep linkurl]} continue
+	    $ctext tag delete link$linknum
+	    $ctext tag add link$linknum "$start + $s c" "$start + $e c"
+	    seturllink $linkurl link$linknum
+	    incr linknum
+	    break
+	}
+    }
 }
 
 proc setlink {id lk} {
@@ -6726,6 +6750,53 @@ proc setlink {id lk} {
     }
 }
 
+proc get_link_config {} {
+    if {[catch {exec git config -z --get-regexp {^linkify\.}} linkers]} {
+	return {}
+    }
+
+    set linktypes [list]
+    foreach item [split $linkers "\0"] {
+	if {$item == ""} continue
+	if {![regexp {linkify\.(\S+)\.(regexp|subst)\s(.*)} $item _ k t v]} {
+	    continue
+	}
+	set linkconfig($t,$k) $v
+	if {$t == "regexp"} { lappend linktypes $k }
+    }
+
+    set linkmakers [list]
+    foreach k $linktypes {
+	if {![info exists linkconfig(subst,$k)]} {
+	    puts stderr "Warning: link `$k' is missing a substitution string"
+	} elseif {[catch {regexp -inline -- $linkconfig(regexp,$k) ""} err]} {
+	    puts stderr "Warning: link `$k': $err"
+	} else {
+	    lappend linkmakers $linkconfig(regexp,$k) $linkconfig(subst,$k)
+	}
+	unset linkconfig(regexp,$k)
+	unset -nocomplain linkconfig(subst,$k)
+    }
+    foreach k [array names linkconfig] {
+	regexp "subst,(.*)" $k _ k
+	puts stderr "Warning: link `$k' is missing a regular expression"
+    }
+    set linkmakers
+}
+
+proc openlink {url} {
+    exec git web--browse --config=gitk.browser $url &
+}
+
+proc seturllink {url lk} {
+    set qurl [string map {% %%} $url]
+    global ctext
+    $ctext tag conf $lk -foreground blue -underline 1
+    $ctext tag bind $lk <1> [list openlink $qurl]
+    $ctext tag bind $lk <Enter> {linkcursor %W 1}
+    $ctext tag bind $lk <Leave> {linkcursor %W -1}
+}
+
 proc appendshortlink {id {pre {}} {post {}}} {
     global ctext linknum
 
@@ -11693,6 +11764,8 @@ if {[tk windowingsystem] eq "win32"} {
     focus -force .
 }
 
+set linkmakers [get_link_config]
+
 getcommits {}
 
 # Local variables:
-- 
1.7.2.5