[PATCH v2] gc: save log from daemonized gc --auto and print it next time

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

While commit 9f673f9 (gc: config option for running --auto in
background - 2014-02-08) helps reduce some complaints about 'gc
--auto' hogging the terminal, it creates another set of problems.

The latest in this set is, as the result of daemonizing, stderr is
closed and all warnings are lost. This warning at the end of cmd_gc()
is particularly important because it tells the user how to avoid "gc
--auto" running repeatedly. Because stderr is closed, the user does
not know, naturally they complain about 'gc --auto' wasting CPU.

Besides reverting 9f673f9 and looking at the problem from another
angle, we could save the stderr in $GIT_DIR/gc.log. Next time, 'gc
--auto' will print the saved warnings, delete gc.log and exit.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 The test is dropped. It does not feel good enough.. The rest of
 changes is minor
 
  diff --git a/builtin/gc.c b/builtin/gc.c
  index 07769a9..3886937 100644
  --- a/builtin/gc.c
  +++ b/builtin/gc.c
  @@ -32,8 +32,6 @@ static int aggressive_window = 250;
   static int gc_auto_threshold = 6700;
   static int gc_auto_pack_limit = 50;
   static int detach_auto = 1;
  -static struct strbuf log_filename = STRBUF_INIT;
  -static int daemonized;
   static const char *prune_expire = "2.weeks.ago";
   
   static struct argv_array pack_refs_cmd = ARGV_ARRAY_INIT;
  @@ -43,6 +41,8 @@ static struct argv_array prune = ARGV_ARRAY_INIT;
   static struct argv_array rerere = ARGV_ARRAY_INIT;
   
   static char *pidfile;
  +static struct strbuf log_filename = STRBUF_INIT;
  +static int daemonized;
   
   static void remove_pidfile(void)
   {
  @@ -338,7 +338,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
   			struct strbuf sb = STRBUF_INIT;
   
   			if (strbuf_read_file(&sb, git_path("gc.log"), 0) > 0) {
  -				warning(_("Last gc run reported the following, gc skipped"));
  +				warning(_("skipping gc; last gc reported:"));
   				fputs(sb.buf, stderr);
   				strbuf_release(&sb);
   				/* let the next gc --auto run as usual */
  @@ -352,8 +352,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
   			 * failure to daemonize is ok, we'll continue
   			 * in foreground
   			 */
  -			if (!daemonize())
  -				daemonized = 1;
  +			daemonized = !daemonize();
   		}
   	} else
   		add_repack_all_option();

 builtin/gc.c | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/builtin/gc.c b/builtin/gc.c
index 5c634af..3886937 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -41,9 +41,20 @@ static struct argv_array prune = ARGV_ARRAY_INIT;
 static struct argv_array rerere = ARGV_ARRAY_INIT;
 
 static char *pidfile;
+static struct strbuf log_filename = STRBUF_INIT;
+static int daemonized;
 
 static void remove_pidfile(void)
 {
+	if (daemonized && log_filename.len) {
+		struct stat st;
+
+		close(2);
+		if (stat(log_filename.buf, &st) ||
+		    !st.st_size ||
+		    rename(log_filename.buf, git_path("gc.log")))
+			unlink(log_filename.buf);
+	}
 	if (pidfile)
 		unlink(pidfile);
 }
@@ -324,13 +335,24 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 			fprintf(stderr, _("See \"git help gc\" for manual housekeeping.\n"));
 		}
 		if (detach_auto) {
+			struct strbuf sb = STRBUF_INIT;
+
+			if (strbuf_read_file(&sb, git_path("gc.log"), 0) > 0) {
+				warning(_("skipping gc; last gc reported:"));
+				fputs(sb.buf, stderr);
+				strbuf_release(&sb);
+				/* let the next gc --auto run as usual */
+				unlink(git_path("gc.log"));
+				return 0;
+			}
+
 			if (gc_before_repack())
 				return -1;
 			/*
 			 * failure to daemonize is ok, we'll continue
 			 * in foreground
 			 */
-			daemonize();
+			daemonized = !daemonize();
 		}
 	} else
 		add_repack_all_option();
@@ -343,6 +365,18 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 		    name, (uintmax_t)pid);
 	}
 
+	if (daemonized) {
+		int fd;
+
+		strbuf_addstr(&log_filename, git_path("gc.log_XXXXXX"));
+		fd = xmkstemp(log_filename.buf);
+		if (fd >= 0) {
+			dup2(fd, 2);
+			close(fd);
+		} else
+			strbuf_release(&log_filename);
+	}
+
 	if (gc_before_repack())
 		return -1;
 
-- 
2.3.0.rc1.137.g477eb31