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git-merge-tree: generalize the "traverse <n> trees in sync" functionality

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It's actually very useful for other things too. Notably, we could do the
combined diff a lot more efficiently with this.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Linus Torvalds 2006-02-15 19:25:32 -08:00 committed by Junio C Hamano
parent 01df529722
commit 164dcb97f0
1 changed files with 73 additions and 59 deletions
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132
merge-tree.c
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@ -125,44 +125,19 @@ static void unresolved(const char *base, struct name_entry n[3])
printf("3 %06o %s %s%s\n", n[2].mode, sha1_to_hex(n[2].sha1), base, n[2].path);
}
/*
* Merge two trees together (t[1] and t[2]), using a common base (t[0])
* as the origin.
*
* This walks the (sorted) trees in lock-step, checking every possible
* name. Note that directories automatically sort differently from other
* files (see "base_name_compare"), so you'll never see file/directory
* conflicts, because they won't ever compare the same.
*
* IOW, if a directory changes to a filename, it will automatically be
* seen as the directory going away, and the filename being created.
*
* Think of this as a three-way diff.
*
* The output will be either:
* - successful merge
* "0 mode sha1 filename"
* NOTE NOTE NOTE! FIXME! We really really need to walk the index
* in parallel with this too!
*
* - conflict:
* "1 mode sha1 filename"
* "2 mode sha1 filename"
* "3 mode sha1 filename"
* where not all of the 1/2/3 lines may exist, of course.
*
* The successful merge rules are the same as for the three-way merge
* in git-read-tree.
*/
static void merge_trees(struct tree_desc t[3], const char *base)
typedef void (*traverse_callback_t)(int n, unsigned long mask, struct name_entry *entry, const char *base);
static void traverse_trees(int n, struct tree_desc *t, const char *base, traverse_callback_t callback)
{
struct name_entry *entry = xmalloc(n*sizeof(*entry));
for (;;) {
struct name_entry entry[3];
unsigned int mask = 0;
unsigned long mask = 0;
int i, last;
last = -1;
for (i = 0; i < 3; i++) {
for (i = 0; i < n; i++) {
if (!t[i].size)
continue;
entry_extract(t+i, entry+i);
@ -182,7 +157,7 @@ static void merge_trees(struct tree_desc t[3], const char *base)
if (cmp < 0)
mask = 0;
}
mask |= 1u << i;
mask |= 1ul << i;
last = i;
}
if (!mask)
@ -192,38 +167,77 @@ static void merge_trees(struct tree_desc t[3], const char *base)
* Update the tree entries we've walked, and clear
* all the unused name-entries.
*/
for (i = 0; i < 3; i++) {
if (mask & (1u << i)) {
for (i = 0; i < n; i++) {
if (mask & (1ul << i)) {
update_tree_entry(t+i);
continue;
}
entry_clear(entry + i);
}
/* Same in both? */
if (same_entry(entry+1, entry+2)) {
if (entry[0].sha1) {
resolve(base, NULL, entry+1);
continue;
}
}
if (same_entry(entry+0, entry+1)) {
if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
resolve(base, entry+1, entry+2);
continue;
}
}
if (same_entry(entry+0, entry+2)) {
if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
resolve(base, NULL, entry+1);
continue;
}
}
unresolved(base, entry);
callback(n, mask, entry, base);
}
free(entry);
}
/*
* Merge two trees together (t[1] and t[2]), using a common base (t[0])
* as the origin.
*
* This walks the (sorted) trees in lock-step, checking every possible
* name. Note that directories automatically sort differently from other
* files (see "base_name_compare"), so you'll never see file/directory
* conflicts, because they won't ever compare the same.
*
* IOW, if a directory changes to a filename, it will automatically be
* seen as the directory going away, and the filename being created.
*
* Think of this as a three-way diff.
*
* The output will be either:
* - successful merge
* "0 mode sha1 filename"
* NOTE NOTE NOTE! FIXME! We really really need to walk the index
* in parallel with this too!
*
* - conflict:
* "1 mode sha1 filename"
* "2 mode sha1 filename"
* "3 mode sha1 filename"
* where not all of the 1/2/3 lines may exist, of course.
*
* The successful merge rules are the same as for the three-way merge
* in git-read-tree.
*/
static void threeway_callback(int n, unsigned long mask, struct name_entry *entry, const char *base)
{
/* Same in both? */
if (same_entry(entry+1, entry+2)) {
if (entry[0].sha1) {
resolve(base, NULL, entry+1);
return;
}
}
if (same_entry(entry+0, entry+1)) {
if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
resolve(base, entry+1, entry+2);
return;
}
}
if (same_entry(entry+0, entry+2)) {
if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
resolve(base, NULL, entry+1);
return;
}
}
unresolved(base, entry);
}
static void merge_trees(struct tree_desc t[3], const char *base)
{
traverse_trees(3, t, base, threeway_callback);
}
static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)