git-sh-i18n--envsubst: our own envsubst(1) for eval_gettext()

Add a git-sh-i18n--envsubst program which is a stripped-down version
of the GNU envsubst(1) program that comes with GNU gettext for use in
the eval_gettext() fallback.

We need a C helper program because implementing eval_gettext() purely
in shell turned out to be unworkable. Digging through the Git mailing
list archives will reveal two shell implementations of eval_gettext
that are almost good enough, but fail on an edge case which is tested
for in the tests which are part of this patch.

These are the modifications I made to envsubst.c as I turned it into
sh-i18n--envsubst.c:

 * Added our git-compat-util.h header for xrealloc() and friends.

 * Removed inclusion of gettext-specific headers.

 * Removed most of main() and replaced it with my own. The modified
   version only does option parsing for --variables. That's all it
   needs.

 * Modified error() invocations to use our error() instead of
   error(3).

 * Replaced the gettext XNMALLOC(n, size) macro with just
   xmalloc(n). Since XNMALLOC() only allocated char's.

 * Removed the string_list_destroy function. It's redundant (also in
   the upstream code).

 * Replaced the use of stdbool.h (a C99 header) by doing the following
   replacements on the code:

    * s/bool/unsigned short int/g
    * s/true/1/g
    * s/false/0/g

Reported-by: Johannes Sixt <j.sixt@viscovery.net>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index ef57c1c9b4..87c83cb458 100644
--- a/Makefile
+++ b/Makefile
@@ -414,6 +414,7 @@ PROGRAM_OBJS += shell.o
 PROGRAM_OBJS += show-index.o
 PROGRAM_OBJS += upload-pack.o
 PROGRAM_OBJS += http-backend.o
+PROGRAM_OBJS += sh-i18n--envsubst.o
 
 PROGRAMS += $(patsubst %.o,git-%$X,$(PROGRAM_OBJS))