Make the pack-refs interfaces usable from outside

This just basically creates a "pack_refs()" function that could be used by
anybody. You pass it in the flags you want as a bitmask (PACK_REFS_ALL and
PACK_REFS_PRUNE), and it will do all the heavy lifting.

Of course, it's still static, and it's all in the builtin-pack-refs.c
file, so it's not actually visible to the outside, but the next step would
be to just move it all to a library file (probably refs.c) and expose it.

Then we could easily make "git gc" do this too.

While I did it, I also made it check the return value of the fflush and
fsync stage, to make sure that we don't overwrite the old packed-refs file
with something that got truncated due to write errors!

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-pack-refs.c

@@ -12,9 +12,11 @@ struct ref_to_prune {
 	char name[FLEX_ARRAY];
 };
 
+#define PACK_REFS_PRUNE	0x0001
+#define PACK_REFS_ALL	0x0002
+
 struct pack_refs_cb_data {
-	int prune;
-	int all;
+	unsigned int flags;
 	struct ref_to_prune *ref_to_prune;
 	FILE *refs_file;
 };
@@ -39,7 +41,7 @@ static int handle_one_ref(const char *path, const unsigned char *sha1,
 	is_tag_ref = !prefixcmp(path, "refs/tags/");
 
 	/* ALWAYS pack refs that were already packed or are tags */
-	if (!cb->all && !is_tag_ref && !(flags & REF_ISPACKED))
+	if (!(cb->flags & PACK_REFS_ALL) && !is_tag_ref && !(flags & REF_ISPACKED))
 		return 0;
 
 	fprintf(cb->refs_file, "%s %s\n", sha1_to_hex(sha1), path);
@@ -53,7 +55,7 @@ static int handle_one_ref(const char *path, const unsigned char *sha1,
 		}
 	}
 
-	if (cb->prune && !do_not_prune(flags)) {
+	if ((cb->flags & PACK_REFS_PRUNE) && !do_not_prune(flags)) {
 		int namelen = strlen(path) + 1;
 		struct ref_to_prune *n = xcalloc(1, sizeof(*n) + namelen);
 		hashcpy(n->sha1, sha1);
@@ -85,26 +87,51 @@ static void prune_refs(struct ref_to_prune *r)
 
 static struct lock_file packed;
 
-int cmd_pack_refs(int argc, const char **argv, const char *prefix)
+static int pack_refs(unsigned int flags)
 {
-	int fd, i;
+	int fd;
 	struct pack_refs_cb_data cbdata;
 
 	memset(&cbdata, 0, sizeof(cbdata));
+	cbdata.flags = flags;
+
+	fd = hold_lock_file_for_update(&packed, git_path("packed-refs"), 1);
+	cbdata.refs_file = fdopen(fd, "w");
+	if (!cbdata.refs_file)
+		die("unable to create ref-pack file structure (%s)",
+		    strerror(errno));
+
+	/* perhaps other traits later as well */
+	fprintf(cbdata.refs_file, "# pack-refs with: peeled \n");
+
+	for_each_ref(handle_one_ref, &cbdata);
+	if (fflush(cbdata.refs_file) || fsync(fd) || fclose(cbdata.refs_file))
+		die("failed to write ref-pack file (%s)", strerror(errno));
+	if (commit_lock_file(&packed) < 0)
+		die("unable to overwrite old ref-pack file (%s)", strerror(errno));
+	if (cbdata.flags & PACK_REFS_PRUNE)
+		prune_refs(cbdata.ref_to_prune);
+	return 0;
+}
 
-	cbdata.prune = 1;
+int cmd_pack_refs(int argc, const char **argv, const char *prefix)
+{
+	int i;
+	unsigned int flags;
+
+	flags = PACK_REFS_PRUNE;
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];
 		if (!strcmp(arg, "--prune")) {
-			cbdata.prune = 1; /* now the default */
+			flags |= PACK_REFS_PRUNE; /* now the default */
 			continue;
 		}
 		if (!strcmp(arg, "--no-prune")) {
-			cbdata.prune = 0;
+			flags &= ~PACK_REFS_PRUNE;
 			continue;
 		}
 		if (!strcmp(arg, "--all")) {
-			cbdata.all = 1;
+			flags |= PACK_REFS_ALL;
 			continue;
 		}
 		/* perhaps other parameters later... */
@@ -113,22 +140,5 @@ int cmd_pack_refs(int argc, const char **argv, const char *prefix)
 	if (i != argc)
 		usage(builtin_pack_refs_usage);
 
-	fd = hold_lock_file_for_update(&packed, git_path("packed-refs"), 1);
-	cbdata.refs_file = fdopen(fd, "w");
-	if (!cbdata.refs_file)
-		die("unable to create ref-pack file structure (%s)",
-		    strerror(errno));
-
-	/* perhaps other traits later as well */
-	fprintf(cbdata.refs_file, "# pack-refs with: peeled \n");
-
-	for_each_ref(handle_one_ref, &cbdata);
-	fflush(cbdata.refs_file);
-	fsync(fd);
-	fclose(cbdata.refs_file);
-	if (commit_lock_file(&packed) < 0)
-		die("unable to overwrite old ref-pack file (%s)", strerror(errno));
-	if (cbdata.prune)
-		prune_refs(cbdata.ref_to_prune);
-	return 0;
+	return pack_refs(flags);
 }