[PATCH] gc: remove gc.pid file at end of execution

[Matthieu Moy <Matthieu.Moy@imag.fr>]

This file isn't really harmful, but isn't useful either, and can create
minor annoyance for the user:

* It's confusing, as the presence of a *.pid file often implies that a
  process is currently running. A user running "ls .git/" and finding
  this file may incorrectly guess that a "git gc" is currently running.

* Leaving this file means that a "git gc" in an already gc-ed repo is
  no-longer a no-op. A user running "git gc" in a set of repositories,
  and then synchronizing this set (e.g. rsync -av, unison, ...) will see
  all the gc.pid files as changed, which creates useless noise.

This patch unlinks the file after the garbage collection is done, so that
gc.pid is actually present only during execution.

Future versions of Git may want to use the information left in the gc.pid
file (e.g. for policies like "don't attempt to run a gc if one has
already been ran less than X hours ago"). If so, this patch can safely be
reverted. For now, let's not bother the users.

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
---
 builtin/gc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/builtin/gc.c b/builtin/gc.c
index 891a2c2..db39963 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -316,5 +316,9 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 		warning(_("There are too many unreachable loose objects; "
 			"run 'git prune' to remove them."));
 
+	/*
+	 * The file isn't harmful, but isn't useful either.
+	 */
+	unlink(git_path("gc.pid"));
 	return 0;
 }
-- 
1.8.4.474.g128a96c