[PATCH RFC] kconfig: place git SHA1 in .config output if in git tree

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

This patch appends the SHA1 hash of the current git tree to the
kernel version line, or "[Not git tree]" if run from a non-git tree.
Uses "git log" to print the hash.

Suggested-by: Ingo Molnar <mingo@elte.hu>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---

 confdata.c |   13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
index c4dec80..4bd7842 100644
--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -399,10 +399,11 @@ int conf_read(const char *name)
 int conf_write(const char *name)
 {
 	FILE *out;
+	FILE *git;
 	struct symbol *sym;
 	struct menu *menu;
 	const char *basename;
-	char dirname[128], tmpname[128], newname[128];
+	char dirname[128], tmpname[128], newname[128], gitsha[128];
 	int type, l;
 	const char *str;
 	time_t now;
@@ -450,12 +451,20 @@ int conf_write(const char *name)
 	if (env && *env)
 		use_timestamp = 0;
 
+	gitsha[0] = '\0';
+	git = popen("git log --pretty=format:%h -1 2> /dev/null", "r");
+	if (git != NULL) {
+		fscanf(git, " %127s ", gitsha);
+		pclose(git);
+	}
+
 	fprintf(out, _("#\n"
 		       "# Automatically generated make config: don't edit\n"
-		       "# Linux kernel version: %s\n"
+		       "# Linux kernel version: %s %s\n"
 		       "%s%s"
 		       "#\n"),
 		     sym_get_string_value(sym),
+		     gitsha[0] == '\0' ? "[Not git tree]" : gitsha,
 		     use_timestamp ? "# " : "",
 		     use_timestamp ? ctime(&now) : "");