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[PATCH] read-tree: save more user hassles during fast-forward.

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This implements the "never lose the current cache information or
the work tree state, but favor a successful merge over merge
failure" principle in the fast-forward two-tree merge operation.

It comes with a set of tests to cover all the cases described in
the case matrix found in the new documentation.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Junio C Hamano
2005-06-07 11:36:30 -07:00
committed by Linus Torvalds
parent 63aff4fed9
commit c859600954
4 changed files with 698 additions and 13 deletions
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49
read-tree.c
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@ -155,28 +155,51 @@ static int threeway_merge(struct cache_entry *stages[4], struct cache_entry **ds
/*
* Two-way merge.
*
* The rule is:
* - every current entry has to match the old tree
* - if the current entry matches the new tree, we leave it
* as-is. Otherwise we require that it be up-to-date.
* The rule is to "carry forward" what is in the index without losing
* information across a "fast forward", favoring a successful merge
* over a merge failure when it makes sense. For details of the
* "carry forward" rule, please see <Documentation/git-read-tree.txt>.
*
*/
static int twoway_merge(struct cache_entry **src, struct cache_entry **dst)
{
struct cache_entry *old = src[0];
struct cache_entry *a = src[1], *b = src[2];
struct cache_entry *current = src[0];
struct cache_entry *oldtree = src[1], *newtree = src[2];
if (src[3])
return -1;
if (old) {
if (!a || !same(old, a))
if (current) {
if ((!oldtree && !newtree) || /* 4 and 5 */
(!oldtree && newtree &&
same(current, newtree)) || /* 6 and 7 */
(oldtree && newtree &&
same(oldtree, newtree)) || /* 14 and 15 */
(oldtree && newtree &&
!same(oldtree, newtree) && /* 18 and 19*/
same(current, newtree))) {
*dst++ = current;
return 1;
}
else if (oldtree && !newtree && same(current, oldtree)) {
/* 10 or 11 */
verify_uptodate(current);
return 0;
}
else if (oldtree && newtree &&
same(current, oldtree) && !same(current, newtree)) {
/* 20 or 21 */
verify_uptodate(current);
return merged_entry(newtree, NULL, dst);
}
else
/* all other failures */
return -1;
}
if (b)
return merged_entry(b, old, dst);
if (old)
verify_uptodate(old);
return 0;
else if (newtree)
return merged_entry(newtree, NULL, dst);
else
return 0;
}
/*