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/*
* GIT - The information manager from hell
*
* Copyright (C) Linus Torvalds, 2005
*/
#include "cache.h"
static int stage = 0;
static int unpack_tree(unsigned char *sha1)
{
void *buffer;
unsigned long size;
buffer = read_object_with_reference(sha1, "tree", &size, 0);
if (!buffer)
return -1;
return read_tree(buffer, size, stage);
}
static char *lockfile_name;
static void remove_lock_file(void)
{
if (lockfile_name)
unlink(lockfile_name);
}
static int path_matches(struct cache_entry *a, struct cache_entry *b)
{
int len = ce_namelen(a);
return ce_namelen(b) == len &&
!memcmp(a->name, b->name, len);
}
static int same(struct cache_entry *a, struct cache_entry *b)
{
return a->ce_mode == b->ce_mode &&
!memcmp(a->sha1, b->sha1, 20);
}
/*
* This removes all trivial merges that don't change the tree
* and collapses them to state 0.
*
* _Any_ other merge is left to user policy. That includes "both
* created the same file", and "both removed the same file" - which are
* trivial, but the user might still want to _note_ it.
*/
static struct cache_entry *merge_entries(struct cache_entry *a,
struct cache_entry *b,
struct cache_entry *c)
{
int len = ce_namelen(a);
/*
* Are they all the same filename? We won't do
* any name merging
*/
if (ce_namelen(b) != len ||
ce_namelen(c) != len ||
memcmp(a->name, b->name, len) ||
memcmp(a->name, c->name, len))
return NULL;
/*
* Ok, all three entries describe the same
* filename, but maybe the contents or file
* mode have changed?
*
* The trivial cases end up being the ones where two
* out of three files are the same:
* - both destinations the same, trivially take either
* - one of the destination versions hasn't changed,
* take the other.
*
* The "all entries exactly the same" case falls out as
* a special case of any of the "two same" cases.
*
* Here "a" is "original", and "b" and "c" are the two
* trees we are merging.
*/
if (same(b,c))
return c;
if (same(a,b))
return c;
if (same(a,c))
return b;
return NULL;
}
static void trivially_merge_cache(struct cache_entry **src, int nr)
{
static struct cache_entry null_entry;
struct cache_entry **dst = src;
struct cache_entry *old = &null_entry;
while (nr) {
struct cache_entry *ce, *result;
ce = src[0];
/* We throw away original cache entries except for the stat information */
if (!ce_stage(ce)) {
old = ce;
src++;
nr--;
active_nr--;
continue;
}
if (nr > 2 && (result = merge_entries(ce, src[1], src[2])) != NULL) {
/*
* See if we can re-use the old CE directly?
* That way we get the uptodate stat info.
*/
if (path_matches(result, old) && same(result, old))
*result = *old;
ce = result;
ce->ce_flags &= ~htons(CE_STAGEMASK);
src += 2;
nr -= 2;
active_nr -= 2;
}
*dst++ = ce;
src++;
nr--;
}
}
static void merge_stat_info(struct cache_entry **src, int nr)
{
static struct cache_entry null_entry;
struct cache_entry **dst = src;
struct cache_entry *old = &null_entry;
while (nr) {
struct cache_entry *ce;
ce = src[0];
/* We throw away original cache entries except for the stat information */
if (!ce_stage(ce)) {
old = ce;
src++;
nr--;
active_nr--;
continue;
}
if (path_matches(ce, old) && same(ce, old))
*ce = *old;
ce->ce_flags &= ~htons(CE_STAGEMASK);
*dst++ = ce;
src++;
nr--;
}
}
static char *read_tree_usage = "read-tree (<sha> | -m <sha1> [<sha2> <sha3>])";
int main(int argc, char **argv)
{
int i, newfd, merge;
unsigned char sha1[20];
static char lockfile[MAXPATHLEN+1];
const char *indexfile = get_index_file();
snprintf(lockfile, sizeof(lockfile), "%s.lock", indexfile);
newfd = open(lockfile, O_RDWR | O_CREAT | O_EXCL, 0600);
if (newfd < 0)
die("unable to create new cachefile");
atexit(remove_lock_file);
lockfile_name = lockfile;
merge = 0;
for (i = 1; i < argc; i++) {
const char *arg = argv[i];
/* "-m" stands for "merge", meaning we start in stage 1 */
if (!strcmp(arg, "-m")) {
int i;
if (stage)
die("-m needs to come first");
read_cache();
for (i = 0; i < active_nr; i++) {
if (ce_stage(active_cache[i]))
die("you need to resolve your current index first");
}
stage = 1;
merge = 1;
continue;
}
if (get_sha1_hex(arg, sha1) < 0)
usage(read_tree_usage);
if (stage > 3)
usage(read_tree_usage);
if (unpack_tree(sha1) < 0)
die("failed to unpack tree object %s", arg);
stage++;
}
if (merge) {
switch (stage) {
case 4: /* Three-way merge */
trivially_merge_cache(active_cache, active_nr);
break;
case 2: /* Just read a tree, merge with old cache contents */
merge_stat_info(active_cache, active_nr);
break;
default:
die("just how do you expect me to merge %d trees?", stage-1);
}
}
if (write_cache(newfd, active_cache, active_nr) || rename(lockfile, indexfile))
die("unable to write new index file");
lockfile_name = NULL;
return 0;
}
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