From 2759cbc7741d7ce7bf44c2433fa1312d3fc7e64a Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 18 Oct 2005 11:35:17 -0700 Subject: [PATCH] git-fetch-pack: avoid unnecessary zero packing If everything is up-to-date locally, we don't need to even ask for a pack-file from the remote, or try to unpack it. This is especially important for tags - since the pack-file common commit logic is based purely on the commit history, it will never be able to find a common tag, and will thus always end up re-fetching them. Especially notably, if the tag points to a non-commit (eg a tagged tree), the pack-file would be unnecessarily big, just because it cannot any most recent common point between commits for pruning. Short-circuiting the case where we already have that reference means that we avoid a lot of these in the common case. NOTE! This only matches remote ref names against the same local name, which works well for tags, but is not as generic as it could be. If we ever need to, we could match against _any_ local ref (if we have it, we have it), but this "match against same name" is simpler and more efficient, and covers the common case. Renaming of refs is common for branch heads, but since those are always commits, the pack-file generation can optimize that case. In some cases we might still end up fetching pack-files unnecessarily, but this at least avoids the re-fetching of tags over and over if you use a regular git fetch --tags ... which was the main reason behind the change. Signed-off-by: Linus Torvalds Signed-off-by: Junio C Hamano --- fetch-pack.c | 50 ++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 44 insertions(+), 6 deletions(-) diff --git a/fetch-pack.c b/fetch-pack.c index 953c0cf44..459736909 100644 --- a/fetch-pack.c +++ b/fetch-pack.c @@ -12,6 +12,7 @@ static const char *exec = "git-upload-pack"; static int find_common(int fd[2], unsigned char *result_sha1, struct ref *refs) { + int fetching; static char line[1000]; int count = 0, flushes = 0, retval; FILE *revs; @@ -20,16 +21,19 @@ static int find_common(int fd[2], unsigned char *result_sha1, if (!revs) die("unable to run 'git-rev-list'"); - while (refs) { + fetching = 0; + for ( ; refs ; refs = refs->next) { unsigned char *remote = refs->old_sha1; - if (verbose) - fprintf(stderr, - "want %s (%s)\n", sha1_to_hex(remote), - refs->name); + unsigned char *local = refs->new_sha1; + + if (!memcmp(remote, local, 20)) + continue; packet_write(fd[1], "want %s\n", sha1_to_hex(remote)); - refs = refs->next; + fetching++; } packet_flush(fd[1]); + if (!fetching) + return 1; flushes = 1; retval = -1; while (fgets(line, sizeof(line), revs) != NULL) { @@ -74,6 +78,35 @@ static int find_common(int fd[2], unsigned char *result_sha1, return retval; } +static int everything_local(struct ref *refs) +{ + int retval; + + for (retval = 1; refs ; refs = refs->next) { + const unsigned char *remote = refs->old_sha1; + unsigned char local[20]; + + if (read_ref(git_path("%s", refs->name), local) < 0 || + memcmp(remote, local, 20)) { + retval = 0; + if (!verbose) + continue; + fprintf(stderr, + "want %s (%s)\n", sha1_to_hex(remote), + refs->name); + continue; + } + + memcpy(refs->new_sha1, local, 20); + if (!verbose) + continue; + fprintf(stderr, + "already have %s (%s)\n", sha1_to_hex(remote), + refs->name); + } + return retval; +} + static int fetch_pack(int fd[2], int nr_match, char **match) { struct ref *ref; @@ -86,6 +119,10 @@ static int fetch_pack(int fd[2], int nr_match, char **match) packet_flush(fd[1]); die("no matching remote head"); } + if (everything_local(ref)) { + packet_flush(fd[1]); + goto all_done; + } if (find_common(fd, sha1, ref) < 0) fprintf(stderr, "warning: no common commits\n"); pid = fork(); @@ -109,6 +146,7 @@ static int fetch_pack(int fd[2], int nr_match, char **match) int code = WEXITSTATUS(status); if (code) die("git-unpack-objects died with error code %d", code); +all_done: while (ref) { printf("%s %s\n", sha1_to_hex(ref->old_sha1), ref->name); -- 2.30.2