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authorMichael Haggerty <mhagger@alum.mit.edu>2013-04-22 21:52:29 +0200
committerJunio C Hamano <gitster@pobox.com>2013-05-01 15:33:10 -0700
commit694b7a1999fa331e00ed9297f3b6b01f7da7a104 (patch)
treede2b4beb210056fb0d30953b0c75186d7f30715a /refs.c
parentc995de61cd218f7ce5119d340ac7d8282b2e2d73 (diff)
downloadgit-694b7a1999fa331e00ed9297f3b6b01f7da7a104.tar.gz
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 <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'refs.c')
-rw-r--r--refs.c23
1 files changed, 23 insertions, 0 deletions
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);
}