From a21d598e0a32eb460b8726596f89d267b6478a98 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 ed5960e6b378a9..a0517885f03606 100644
--- a/Makefile
+++ b/Makefile
@@ -1882,7 +1882,9 @@ 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 df1332fa3c977d..6ebea665780b7e 100644
--- a/help.c
+++ b/help.c
@@ -413,6 +413,8 @@ int cmd_version(int argc, const char **argv, const char *prefix)
 	printf("git version %s\n", git_version_string);
 
 	if (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 6106a8098c8a46..41b718c29e1b9f 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 6911a4f1558de0..7c62e80577154d 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);