From 694b7a1999fa331e00ed9297f3b6b01f7da7a104 Mon Sep 17 00:00:00 2001 From: Michael Haggerty Date: Mon, 22 Apr 2013 21:52:29 +0200 Subject: [PATCH] repack_without_ref(): write peeled refs in the rewritten file When a reference that existed in the packed-refs file is deleted, the packed-refs file must be rewritten. Previously, the file was rewritten without any peeled refs, even if the file contained peeled refs when it was read. This was not a bug, because the packed-refs file header didn't claim that the file contained peeled values. But it had a performance cost, because the repository would lose the benefit of having precomputed peeled references until pack-refs was run again. Teach repack_without_ref() to write peeled refs to the packed-refs file (regardless of whether they were present in the old version of the file). This means that if the old version of the packed-refs file was not fully peeled, then repack_without_ref() will have to peel references. To avoid the expense of reading lots of loose references, we take two shortcuts relative to pack-refs: * If the peeled value of a reference is already known (i.e., because it was read from the old version of the packed-refs file), then output that peeled value again without any checks. This is the usual code path and should avoid any noticeable overhead. (This is different than pack-refs, which always re-peels references.) * We don't verify that the packed ref is still current. It could be that a packed references is overridden by a loose reference, in which case the packed ref is no longer needed and might even refer to an object that has been garbage collected. But we don't check; instead, we just try to peel all references. If peeling is successful, the peeled value is written out (even though it might not be needed any more); if not, then the reference is silently omitted from the output. The extra overhead of peeling references in repack_without_ref() should only be incurred the first time the packed-refs file is written by a version of Git that knows about the "fully-peeled" attribute. Signed-off-by: Michael Haggerty Signed-off-by: Junio C Hamano --- refs.c | 23 +++++++++++++++++++++++ t/t3211-peel-ref.sh | 2 +- 2 files changed, 24 insertions(+), 1 deletion(-) diff --git a/refs.c b/refs.c index f8f295ea69..6032ba62c7 100644 --- a/refs.c +++ b/refs.c @@ -877,6 +877,13 @@ void invalidate_ref_cache(const char *submodule) #define PEELED_LINE_LENGTH 42 /* + * The packed-refs header line that we write out. Perhaps other + * traits will be added later. The trailing space is required. + */ +static const char PACKED_REFS_HEADER[] = + "# pack-refs with: peeled fully-peeled \n"; + +/* * Parse one line from a packed-refs file. Write the SHA1 to sha1. * Return a pointer to the refname within the line (null-terminated), * or NULL if there was a problem. @@ -1391,6 +1398,12 @@ static enum peel_status peel_object(const unsigned char *name, unsigned char *sh /* * Peel the entry (if possible) and return its new peel_status. + * + * It is OK to call this function with a packed reference entry that + * might be stale and might even refer to an object that has since + * been garbage-collected. In such a case, if the entry has + * REF_KNOWS_PEELED then leave the status unchanged and return + * PEEL_PEELED or PEEL_NON_TAG; otherwise, return PEEL_INVALID. */ static enum peel_status peel_entry(struct ref_entry *entry) { @@ -1993,6 +2006,15 @@ static int repack_ref_fn(struct ref_entry *entry, void *cb_data) if (len > sizeof(line)) die("too long a refname '%s'", entry->name); write_or_die(*fd, line, len); + if (!peel_entry(entry)) { + /* This reference could be peeled; write the peeled value: */ + if (snprintf(line, sizeof(line), "^%s\n", + sha1_to_hex(entry->u.value.peeled)) != + PEELED_LINE_LENGTH) + die("internal error"); + write_or_die(*fd, line, PEELED_LINE_LENGTH); + } + return 0; } @@ -2023,6 +2045,7 @@ static int repack_without_ref(const char *refname) rollback_lock_file(&packlock); return 0; } + write_or_die(fd, PACKED_REFS_HEADER, strlen(PACKED_REFS_HEADER)); do_for_each_entry_in_dir(packed, 0, repack_ref_fn, &fd); return commit_lock_file(&packlock); } diff --git a/t/t3211-peel-ref.sh b/t/t3211-peel-ref.sh index cca1acb184..3b7caca421 100755 --- a/t/t3211-peel-ref.sh +++ b/t/t3211-peel-ref.sh @@ -61,7 +61,7 @@ test_expect_success 'refs are peeled outside of refs/tags (old packed)' ' test_cmp expect actual ' -test_expect_failure 'peeled refs survive deletion of packed ref' ' +test_expect_success 'peeled refs survive deletion of packed ref' ' git pack-refs --all && cp .git/packed-refs fully-peeled && git branch yadda && -- 2.11.4.GIT