Use $GITPERLLIB instead of $RUNNING_GIT_TESTS and centralize @INC munging

This makes the Git perl scripts check $GITPERLLIB instead of
$RUNNING_GIT_TESTS, which makes more sense if you are setting up your shell
environment to use a non-installed Git instance.

It also weeds out the @INC munging from the individual scripts and makes
Makefile add it during the .perl files processing, so that we can change
just a single place when we modify this shared logic. It looks ugly in the
scripts, too. ;-)

And instead of doing arcane things with the @INC array, we just do 'use lib'
instead, which is essentialy the same thing anyway.

I first want to do three separate patches but it turned out that it's quite
a lot neater when bundled together, so I hope it's ok.

Signed-off-by: Petr Baudis <pasky@suse.cz>
Signed-off-by: Junio C Hamano <junkio@cox.net>

INSTALL

@@ -39,8 +39,8 @@ Issues of note:
 
 	GIT_EXEC_PATH=`pwd`
 	PATH=`pwd`:$PATH
-	PERL5LIB=`pwd`/perl/blib/lib:`pwd`/perl/blib/arch/auto/Git
-	export GIT_EXEC_PATH PATH PERL5LIB
+	GITPERLLIB=`pwd`/perl/blib/lib:`pwd`/perl/blib/arch/auto/Git
+	export GIT_EXEC_PATH PATH GITPERLLIB
 
  - Git is reasonably self-sufficient, but does depend on a few external
    programs and libraries:

Makefile

@@ -550,7 +550,9 @@ $(patsubst %.perl,%,$(SCRIPT_PERL)): perl/Makefile
 $(patsubst %.perl,%,$(SCRIPT_PERL)): % : %.perl
 	rm -f $@ $@+
 	INSTLIBDIR=`$(MAKE) -C perl -s --no-print-directory instlibdir` && \
-	sed -e '1s|#!.*perl\(.*\)|#!$(PERL_PATH_SQ)\1|' \
+	sed -e '1s|#!.*perl|#!$(PERL_PATH_SQ)|1' \
+	    -e '2i\
+	        use lib (split(/:/, $$ENV{GITPERLLIB} || '\'"$$INSTLIBDIR"\''));' \
 	    -e 's|@@INSTLIBDIR@@|'"$$INSTLIBDIR"'|g' \
 	    -e 's/@@GIT_VERSION@@/$(GIT_VERSION)/g' \
 	    $@.perl >$@+

git-fmt-merge-msg.perl

@@ -5,11 +5,6 @@
 # Read .git/FETCH_HEAD and make a human readable merge message
 # by grouping branches and tags together to form a single line.
 
-BEGIN {
-	unless (exists $ENV{'RUNNING_GIT_TESTS'}) {
-		unshift @INC, '@@INSTLIBDIR@@';
-	}
-}
 use strict;
 use Git;
 use Error qw(:try);

git-mv.perl

@@ -6,11 +6,6 @@
 # This file is licensed under the GPL v2, or a later version
 # at the discretion of Linus Torvalds.
 
-BEGIN {
-	unless (exists $ENV{'RUNNING_GIT_TESTS'}) {
-		unshift @INC, '@@INSTLIBDIR@@';
-	}
-}
 use warnings;
 use strict;
 use Getopt::Std;

t/test-lib.sh

@@ -206,9 +206,8 @@ PYTHON=`sed -e '1{
 	PYTHONPATH=$(pwd)/../compat
 	export PYTHONPATH
 }
-RUNNING_GIT_TESTS=YesWeAre
-PERL5LIB=$(pwd)/../perl/blib/lib:$(pwd)/../perl/blib/arch/auto/Git
-export PERL5LIB RUNNING_GIT_TESTS
+GITPERLLIB=$(pwd)/../perl/blib/lib:$(pwd)/../perl/blib/arch/auto/Git
+export GITPERLLIB
 test -d ../templates/blt || {
 	error "You haven't built things yet, have you?"
 }