[PATCH v4 1/4] Makefile: generate Perl header from template file

[Dan Jacques <dnj@google.com>]

Currently, the generated Perl script headers are emitted by commands in
the Makefile. This mechanism restricts options to introduce alternative
header content, needed by Perl runtime prefix support, and obscures the
origin of the Perl script header.

Change the Makefile to generate a header by processing a template file and
move the header content into the "perl/" subdirectory. The processed
generated will now be stored in the "GIT-PERL-HEADER" file. This allows
the content of the Perl header to be controlled by changing the path of
the template in the Makefile.

Signed-off-by: Dan Jacques <dnj@google.com>
Thanks-to: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Thanks-to: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 .gitignore                           |  1 +
 Makefile                             | 24 +++++++++++++++---------
 perl/header_fixed_prefix.pl.template |  1 +
 3 files changed, 17 insertions(+), 9 deletions(-)
 create mode 100644 perl/header_fixed_prefix.pl.template

diff --git a/.gitignore b/.gitignore
index 833ef3b0b..89bd7bd8a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,6 +3,7 @@
 /GIT-LDFLAGS
 /GIT-PREFIX
 /GIT-PERL-DEFINES
+/GIT-PERL-HEADER
 /GIT-PYTHON-VARS
 /GIT-SCRIPT-DEFINES
 /GIT-USER-AGENT
diff --git a/Makefile b/Makefile
index e53750ca0..f7c4ac207 100644
--- a/Makefile
+++ b/Makefile
@@ -1964,18 +1964,15 @@ perl/PM.stamp: FORCE
 perl/perl.mak: GIT-CFLAGS GIT-PREFIX perl/Makefile perl/Makefile.PL
 	$(QUIET_SUBDIR0)perl $(QUIET_SUBDIR1) PERL_PATH='$(PERL_PATH_SQ)' prefix='$(prefix_SQ)' $(@F)
 
+PERL_HEADER_TEMPLATE = perl/header_fixed_prefix.pl.template
 PERL_DEFINES = $(PERL_PATH_SQ):$(PERLLIB_EXTRA_SQ)
-$(SCRIPT_PERL_GEN): % : %.perl perl/perl.mak GIT-PERL-DEFINES GIT-VERSION-FILE
+
+$(SCRIPT_PERL_GEN): % : %.perl perl/perl.mak GIT-PERL-DEFINES GIT-PERL-HEADER GIT-VERSION-FILE
 	$(QUIET_GEN)$(RM) $@ $@+ && \
-	INSTLIBDIR=`MAKEFLAGS= $(MAKE) -C perl -s --no-print-directory instlibdir` && \
-	INSTLIBDIR_EXTRA='$(PERLLIB_EXTRA_SQ)' && \
-	INSTLIBDIR="$$INSTLIBDIR$${INSTLIBDIR_EXTRA:+:$$INSTLIBDIR_EXTRA}" && \
 	sed -e '1{' \
 	    -e '	s|#!.*perl|#!$(PERL_PATH_SQ)|' \
-	    -e '	h' \
-	    -e '	s=.*=use lib (split(/$(pathsep)/, $$ENV{GITPERLLIB} || "'"$$INSTLIBDIR"'"));=' \
-	    -e '	H' \
-	    -e '	x' \
+	    -e '	rGIT-PERL-HEADER' \
+	    -e '	G' \
 	    -e '}' \
 	    -e 's/@@GIT_VERSION@@/$(GIT_VERSION)/g' \
 	    $< >$@+ && \
@@ -1989,6 +1986,15 @@ GIT-PERL-DEFINES: FORCE
 		echo "$$FLAGS" >$@; \
 	    fi
 
+GIT-PERL-HEADER: $(PERL_HEADER_TEMPLATE) GIT-PERL-DEFINES perl/perl.mak Makefile
+	$(QUIET_GEN)$(RM) $@ && \
+	INSTLIBDIR=`MAKEFLAGS= $(MAKE) -C perl -s --no-print-directory instlibdir` && \
+	INSTLIBDIR_EXTRA='$(PERLLIB_EXTRA_SQ)' && \
+	INSTLIBDIR="$$INSTLIBDIR$${INSTLIBDIR_EXTRA:+:$$INSTLIBDIR_EXTRA}" && \
+	sed -e 's=@@PATHSEP@@=$(pathsep)=g' \
+	    -e 's=@@INSTLIBDIR@@='$$INSTLIBDIR'=g' \
+	    $< >$@+ && \
+	mv $@+ $@
 
 .PHONY: gitweb
 gitweb:
@@ -2707,7 +2713,7 @@ ifndef NO_TCLTK
 endif
 	$(RM) GIT-VERSION-FILE GIT-CFLAGS GIT-LDFLAGS GIT-BUILD-OPTIONS
 	$(RM) GIT-USER-AGENT GIT-PREFIX
-	$(RM) GIT-SCRIPT-DEFINES GIT-PERL-DEFINES GIT-PYTHON-VARS
+	$(RM) GIT-SCRIPT-DEFINES GIT-PERL-DEFINES GIT-PERL-HEADER GIT-PYTHON-VARS
 
 .PHONY: all install profile-clean clean strip
 .PHONY: shell_compatibility_test please_set_SHELL_PATH_to_a_more_modern_shell
diff --git a/perl/header_fixed_prefix.pl.template b/perl/header_fixed_prefix.pl.template
new file mode 100644
index 000000000..9a4bc4d30
--- /dev/null
+++ b/perl/header_fixed_prefix.pl.template
@@ -0,0 +1 @@
+use lib (split(/@@PATHSEP@@/, $ENV{GITPERLLIB} || "@@INSTLIBDIR@@"));
-- 
2.15.0.chromium12