From aff629b3f9f0beef1256101eee03d44ed029534c Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Fri, 9 Dec 2016 17:48:24 +0100
Subject: [PATCH] version --build-options: report commit, too, if possible

In particular when local tags are used (or tags that are pushed to some
fork) to build Git, it is very hard to figure out from which particular
revision a particular Git executable was built.

Let's just report that in our build options.

We need to be careful, though, to report when the current commit cannot be
determined, e.g. when building from a tarball without any associated Git
repository.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 Makefile  | 4 +++-
 help.c    | 2 ++
 version.c | 1 +
 version.h | 1 +
 4 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index d5454ca336..d615d680ed 100644
--- a/Makefile
+++ b/Makefile
@@ -1772,7 +1772,9 @@ builtin/help.sp builtin/help.s builtin/help.o: EXTRA_CPPFLAGS = \
 version.sp version.s version.o: GIT-VERSION-FILE GIT-USER-AGENT
 version.sp version.s version.o: EXTRA_CPPFLAGS = \
 	'-DGIT_VERSION="$(GIT_VERSION)"' \
-	'-DGIT_USER_AGENT=$(GIT_USER_AGENT_CQ_SQ)'
+	'-DGIT_USER_AGENT=$(GIT_USER_AGENT_CQ_SQ)' \
+	'-DGIT_BUILT_FROM_COMMIT="$(shell git rev-parse -q --verify HEAD || \
+		echo "(unknown)")"'
 
 $(BUILT_INS): git$X
 	$(QUIET_BUILT_IN)$(RM) $@ && \
diff --git a/help.c b/help.c
index 304c3d3601..5f07a53c26 100644
--- a/help.c
+++ b/help.c
@@ -433,6 +433,8 @@ int cmd_version(int argc, const char **argv, const char *prefix)
 	printf("git version %s\n", git_version_string);
 	while (*++argv) {
 		if (!strcmp(*argv, "--build-options")) {
+			printf("built from commit: %s\n",
+			       git_built_from_commit_string);
 			printf("sizeof-long: %d\n", (int)sizeof(long));
 			printf("machine: %s\n", build_platform);
 			/* NEEDSWORK: also save and output GIT-BUILD_OPTIONS? */
diff --git a/version.c b/version.c
index 6106a8098c..41b718c29e 100644
--- a/version.c
+++ b/version.c
@@ -3,6 +3,7 @@
 #include "strbuf.h"
 
 const char git_version_string[] = GIT_VERSION;
+const char git_built_from_commit_string[] = GIT_BUILT_FROM_COMMIT;
 
 const char *git_user_agent(void)
 {
diff --git a/version.h b/version.h
index 6911a4f155..7c62e80577 100644
--- a/version.h
+++ b/version.h
@@ -2,6 +2,7 @@
 #define VERSION_H
 
 extern const char git_version_string[];
+extern const char git_built_from_commit_string[];
 
 const char *git_user_agent(void);
 const char *git_user_agent_sanitized(void);