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fast-import: do less work when given "from" matches current branch head 

When building a fast-import stream, it's easy to forget the fact
that for non-merge commits happening on top of the current branch
head, there is no need for a "from" command. That is corroborated by
the fact that at least git-p4, hg-fast-export and felipec's
git-remote-hg all unconditionally use a "from" command.

Unfortunately, giving a "from" command always resets the branch
tree, forcing it to be re-read, and in many cases, the pack is also
closed and reopened through gfi_unpack_entry.  Both are unnecessary
overhead, and the latter is particularly slow at least on OSX.

Avoid resetting the tree when it's unmodified, and avoid calling
gfi_unpack_entry when the given mark points to the same commit as
the current branch head.

Signed-off-by: Mike Hommey <mh@glandium.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Mike Hommey 2015-07-09 15:50:09 +09:00 committed by Junio C Hamano
parent 7ecec52d42
commit 0df3245721
1 changed files with 17 additions and 12 deletions
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29
fast-import.c
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@ -2588,14 +2588,12 @@ static int parse_from(struct branch *b)
{
const char *from;
struct branch *s;
unsigned char sha1[20];
if (!skip_prefix(command_buf.buf, "from ", &from))
return 0;
if (b->branch_tree.tree) {
release_tree_content_recursive(b->branch_tree.tree);
b->branch_tree.tree = NULL;
}
hashcpy(sha1, b->branch_tree.versions[1].sha1);
s = lookup_branch(from);
if (b == s)
@ -2610,14 +2608,16 @@ static int parse_from(struct branch *b)
struct object_entry *oe = find_mark(idnum);
if (oe->type != OBJ_COMMIT)
die("Mark :%" PRIuMAX " not a commit", idnum);
hashcpy(b->sha1, oe->idx.sha1);
if (oe->pack_id != MAX_PACK_ID) {
unsigned long size;
char *buf = gfi_unpack_entry(oe, &size);
parse_from_commit(b, buf, size);
free(buf);
} else
parse_from_existing(b);
if (hashcmp(b->sha1, oe->idx.sha1)) {
hashcpy(b->sha1, oe->idx.sha1);
if (oe->pack_id != MAX_PACK_ID) {
unsigned long size;
char *buf = gfi_unpack_entry(oe, &size);
parse_from_commit(b, buf, size);
free(buf);
} else
parse_from_existing(b);
}
} else if (!get_sha1(from, b->sha1)) {
parse_from_existing(b);
if (is_null_sha1(b->sha1))
@ -2626,6 +2626,11 @@ static int parse_from(struct branch *b)
else
die("Invalid ref name or SHA1 expression: %s", from);
if (b->branch_tree.tree && hashcmp(sha1, b->branch_tree.versions[1].sha1)) {
release_tree_content_recursive(b->branch_tree.tree);
b->branch_tree.tree = NULL;
}
read_next_command();
return 1;
}