use build-time SHELL_PATH in test scripts

The top-level Makefile now creates a GIT-BUILD-OPTIONS file
which stores any options selected by the make process that
may be of use to further parts of the build process.
Specifically, we store the SHELL_PATH so that it can be used
by tests to construct shell scripts on the fly.

The format of the GIT-BUILD-OPTIONS file is Bourne shell,
and it is sourced by test-lib.sh; all tests can rely on just
having $SHELL_PATH correctly set in the environment.

The GIT-BUILD-OPTIONS file is written every time the
toplevel 'make' is invoked. Since the only users right now
are the test scripts, there's no drawback to updating its
timestamp. If something build-related depends on this, we
can do a trick similar to the one used by GIT-CFLAGS.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

.gitignore

+GIT-BUILD-OPTIONS
 GIT-CFLAGS
 GIT-GUI-VARS
 GIT-VERSION-FILE

Makefile

@@ -812,7 +812,7 @@ export TAR INSTALL DESTDIR SHELL_PATH
 
 ### Build rules
 
-all:: $(ALL_PROGRAMS) $(BUILT_INS) $(OTHER_PROGRAMS)
+all:: $(ALL_PROGRAMS) $(BUILT_INS) $(OTHER_PROGRAMS) GIT-BUILD-OPTIONS
 ifneq (,$X)
 	$(foreach p,$(patsubst %$X,%,$(filter %$X,$(ALL_PROGRAMS) $(BUILT_INS) git$X)), $(RM) '$p';)
 endif
@@ -1011,6 +1011,9 @@ GIT-CFLAGS: .FORCE-GIT-CFLAGS
 		echo "$$FLAGS" >GIT-CFLAGS; \
             fi
 
+GIT-BUILD-OPTIONS: .FORCE-GIT-BUILD-OPTIONS
+	@echo SHELL_PATH=\''$(SHELL_PATH_SQ)'\' >$@
+
 ### Detect Tck/Tk interpreter path changes
 ifndef NO_TCLTK
 TRACK_VARS = $(subst ','\'',-DTCLTK_PATH='$(TCLTK_PATH_SQ)')
@@ -1166,10 +1169,11 @@ ifndef NO_TCLTK
 	$(MAKE) -C gitk-git clean
 	$(MAKE) -C git-gui clean
 endif
-	$(RM) GIT-VERSION-FILE GIT-CFLAGS GIT-GUI-VARS
+	$(RM) GIT-VERSION-FILE GIT-CFLAGS GIT-GUI-VARS GIT-BUILD-OPTIONS
 
 .PHONY: all install clean strip
 .PHONY: .FORCE-GIT-VERSION-FILE TAGS tags cscope .FORCE-GIT-CFLAGS
+.PHONY: .FORCE-GIT-BUILD-OPTIONS
 
 ### Check documentation
 #

t/t3404-rebase-interactive.sh

@@ -61,7 +61,7 @@ test_expect_success 'setup' '
 	git tag I
 '
 
-echo "#!$SHELL" >fake-editor
+echo "#!$SHELL_PATH" >fake-editor.sh
 cat >> fake-editor.sh <<\EOF
 case "$1" in
 */COMMIT_EDITMSG)

t/test-lib.sh

@@ -359,6 +359,8 @@ if ! test -x ../test-chmtime; then
 	exit 1
 fi
 
+. ../GIT-BUILD-OPTIONS
+
 # Test repository
 test=trash
 rm -fr "$test"