[PATCHv2 1/2 (RFC?)] gitweb: Prepare for splitting gitweb

[Jakub Narebski <jnareb@gmail.com>]

Prepare gitweb for being split into modules that would be installed in
$(gitweblibdir), by default alongside gitweb in 'lib/' subdirectory.

Gitweb would search first in 'lib/' subdirectory from where gitweb.cgi
is installed, via

  use lib __DIR__.'/lib';

(This allow for tests to work with source version of gitweb without
changes.)  Then it searches in $(gitweblibdir) directory (set during
build time), by default "$(gitwebdir)/lib", via

  use lib "++GITWEBLIBDIR++";

which is set to requested dir during building of gitweb.cgi.  Note
that 'use lib' assures no trailing duplicate entries in @INC.


This preparatory work allows to add new module to gitweb by simply
adding

  GITWEB_MODULES += <module>

to gitweb/Makefile (assuming that the module is in 'gitweb/lib/'
directory).

While at it pass GITWEBLIBDIR in addition to GITWEB_TEST_INSTALLED to
allow testing installed version of gitweb and installed version of
modules (for future tests which would check individual (sub)modules).


At Pavan Kumar Sankara suggestion gitweb/Makefile uses

  install [OPTION]... SOURCE... DIRECTORY

format (2nd format) with single SOURCE rather than

  install [OPTION]... SOURCE DEST

format (1st format) because of security reasons (race conditions).
Modern GNU install has `-T' / `--no-target-directory' option, but we
cannot rely that the $(INSTALL) we are using supports this option.

The install-modules target in gitweb/Makefile uses shell 'for' loop,
instead of make's $(foreach) function, to avoid possible problem with
generating a command line that exceeded the maximum argument list
length.

Helped-by: Pavan Kumar Sunkara <pavan.sss1991@gmail.com>
Helped-by: Alejandro R. Sedeño <asedeno@mit.edu>
Signed-off-by: Jakub Narębski <jnareb@gmail.com>
---
This patch is closest to

  [PATCH (version C) 1/2] gitweb: Prepare for splitting gitweb
  http://thread.gmane.org/gmane.comp.version-control.git/165824/focus=165826

from previous (v1) version of this series.

  Advantages:
  - can run source version of gitweb (gitweb/gitweb.perl) as a script simply
  - supports relocating gitweb modules (to gitweblibdir)
  - allow users to simply install extra modules by hand alongside gitweb

  Disadvantages:
  - most complicated code of all cases

In this version modules from __DIR__."/lib", i.e. installed alongside
gitweb.cgi take preference over common modules installed in
"++GITWEBLIBDIR++", as suggested / requested by Alejandro:

  http://thread.gmane.org/gmane.comp.version-control.git/165824/focus=165926  


This patch is marked as possible RFC because I am not sure if
"$(gitwebdir)/lib" directory to install modules alongside gitweb.cgi
should be created unconditionally; it might be empty if
$(gitweblibdir) is changed from its default version.

This version also include update to gitweb/INSTALL.


Side-note: I have thought about adding sanity check for empty
"++GITWEBLIBDIR++" in the form of

  use if "++GITWEBLIBDIR++", lib => "++GITWEBLIBDIR++";

or

  use lib "++GITWEBLIBDIR++" || '.';

But because default value of "++GITWEBLIBDIR++" is never empty, I
don't think it is worth complicating code protecting against unlikely
user error; Perl would give the following warning:

  Empty compile time value given to use lib

 gitweb/INSTALL     |    7 +++++++
 gitweb/Makefile    |   20 ++++++++++++++++++--
 gitweb/gitweb.perl |   11 +++++++++++
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/gitweb/INSTALL b/gitweb/INSTALL
index 4964a67..7af343a 100644
--- a/gitweb/INSTALL
+++ b/gitweb/INSTALL
@@ -243,6 +243,13 @@ The following optional Perl modules are required for extra features
  - HTML::TagCloud - for fancy tag cloud in project list view
  - HTTP::Date or Time::ParseDate - to support If-Modified-Since for feeds
 
+Those modules can be installed, in order of search, alongside
+gitweb.cgi in 'lib/' subdirectory, in '$(gitweblibdir)' directory
+(given during build), or in one of directories in which Perl looks for
+library files (PERL5LIB, PERLLIB, standard places, current directory,
+etc.).  Note that the first two places are by default the same
+directory; "$(gitweblibdir)" is "$(gitwebdir)/lib".
+
 
 Example web server configuration
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/gitweb/Makefile b/gitweb/Makefile
index 0a6ac00..b353d15 100644
--- a/gitweb/Makefile
+++ b/gitweb/Makefile
@@ -13,6 +13,7 @@ all::
 prefix ?= $(HOME)
 bindir ?= $(prefix)/bin
 gitwebdir ?= /var/www/cgi-bin
+gitweblibdir ?= $(gitwebdir)/lib
 
 RM ?= rm -f
 INSTALL ?= install
@@ -57,6 +58,7 @@ PERL_PATH  ?= /usr/bin/perl
 bindir_SQ = $(subst ','\'',$(bindir))#'
 gitwebdir_SQ = $(subst ','\'',$(gitwebdir))#'
 gitwebstaticdir_SQ = $(subst ','\'',$(gitwebdir)/static)#'
+gitweblibdir_SQ = $(subst ','\'',$(gitweblibdir))#'
 SHELL_PATH_SQ = $(subst ','\'',$(SHELL_PATH))#'
 PERL_PATH_SQ  = $(subst ','\'',$(PERL_PATH))#'
 DESTDIR_SQ    = $(subst ','\'',$(DESTDIR))#'
@@ -115,6 +117,7 @@ GITWEB_FILES += static/git-logo.png static/git-favicon.png
 GITWEB_REPLACE = \
 	-e 's|++GIT_VERSION++|$(GIT_VERSION)|g' \
 	-e 's|++GIT_BINDIR++|$(bindir)|g' \
+	-e 's|++GITWEBLIBDIR++|$(gitweblibdir)|g' \
 	-e 's|++GITWEB_CONFIG++|$(GITWEB_CONFIG)|g' \
 	-e 's|++GITWEB_CONFIG_SYSTEM++|$(GITWEB_CONFIG_SYSTEM)|g' \
 	-e 's|++GITWEB_HOME_LINK_STR++|$(GITWEB_HOME_LINK_STR)|g' \
@@ -153,20 +156,33 @@ test:
 
 test-installed:
 	GITWEB_TEST_INSTALLED='$(DESTDIR_SQ)$(gitwebdir_SQ)' \
+	GITWEBLIBDIR='$(DESTDIR_SQ)$(gitweblibdir_SQ)' \
 		$(MAKE) -C ../t gitweb-test
 
 ### Installation rules
 
-install: all
+install: all install-modules
 	$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(gitwebdir_SQ)'
 	$(INSTALL) -m 755 $(GITWEB_PROGRAMS) '$(DESTDIR_SQ)$(gitwebdir_SQ)'
 	$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(gitwebstaticdir_SQ)'
 	$(INSTALL) -m 644 $(GITWEB_FILES) '$(DESTDIR_SQ)$(gitwebstaticdir_SQ)'
 
+install-modules:
+	$(INSTALL) -m 755 $(GITWEB_PROGRAMS) '$(DESTDIR_SQ)$(gitwebdir_SQ)/lib'
+	install_dirs="$(sort $(dir $(GITWEB_MODULES)))" && \
+	for dir in $$install_dirs; do \
+		test -d '$(DESTDIR_SQ)$(gitweblibdir_SQ)'/"$$dir" || \
+		$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(gitweblibdir_SQ)'/"$$dir"; \
+	done
+	gitweb_modules="$(GITWEB_MODULES)" && \
+	for mod in $$gitweb_modules; do \
+		$(INSTALL) -m 644 "lib/$$mod" '$(DESTDIR_SQ)$(gitweblibdir_SQ)'/"$$(dirname $$mod)"; \
+	done
+
 ### Cleaning rules
 
 clean:
 	$(RM) gitweb.cgi static/gitweb.min.js static/gitweb.min.css GITWEB-BUILD-OPTIONS
 
-.PHONY: all clean install test test-installed .FORCE-GIT-VERSION-FILE FORCE
+.PHONY: all clean install install-modules test test-installed .FORCE-GIT-VERSION-FILE FORCE
 
diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index ee69ea6..f094471 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -10,6 +10,17 @@
 use 5.008;
 use strict;
 use warnings;
+
+use File::Spec;
+
+# __DIR__ is excerpt from Dir::Self
+sub __DIR__ () {
+	File::Spec->rel2abs(join '', (File::Spec->splitpath(__FILE__))[0, 1]);
+}
+use lib "++GITWEBLIBDIR++";
+use lib __DIR__ . '/lib';
+
+
 use CGI qw(:standard :escapeHTML -nosticky);
 use CGI::Util qw(unescape);
 use CGI::Carp qw(fatalsToBrowser set_message);
-- 
1.7.3