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Make "read-tree" merge the trees it reads by giving them consecutive states. 

Normally you'd use state 0 for the "merged" state, and start out with
state 1 being "origin", state 2 being "first tree" and state 3 being
"second tree".

Once all the index entries are back in state 0, we have a successful
merge and can write the result tree back.
maint
Linus Torvalds 2005-04-15 22:53:45 -07:00
parent 95fd5bf82a
commit d99082e0e3
1 changed files with 53 additions and 6 deletions
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59
read-tree.c
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@ -5,6 +5,8 @@
*/
#include "cache.h"

static int stage = 0;

static int read_one_entry(unsigned char *sha1, const char *base, int baselen, const char *pathname, unsigned mode)
{
int len = strlen(pathname);
@ -14,7 +16,7 @@ static int read_one_entry(unsigned char *sha1, const char *base, int baselen, co
memset(ce, 0, size);

ce->ce_mode = htonl(mode);
ce->ce_flags = htons(baselen + len);
ce->ce_flags = create_ce_flags(baselen + len, stage);
memcpy(ce->name, base, baselen);
memcpy(ce->name + baselen, pathname, len+1);
memcpy(ce->sha1, sha1, 20);
@ -71,6 +73,49 @@ static void remove_lock_file(void)
unlink(".git/index.lock");
}

/*
* This removes all identical entries and collapses them to state 0.
*
* _Any_ other merge (even a trivial one, like both ) 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 int same_entry(struct cache_entry *a,
struct cache_entry *b,
struct cache_entry *c)
{
int len = ce_namelen(a);
return a->ce_mode == b->ce_mode &&
a->ce_mode == c->ce_mode &&
ce_namelen(b) == len &&
ce_namelen(c) == len &&
!memcmp(a->name, b->name, len) &&
!memcmp(a->name, c->name, len) &&
!memcmp(a->sha1, b->sha1, 20) &&
!memcmp(a->sha1, c->sha1, 20);
}

static void trivially_merge_cache(struct cache_entry **src, int nr)
{
struct cache_entry **dst = src;

while (nr) {
struct cache_entry *ce;

ce = src[0];
if (nr > 2 && same_entry(ce, src[1], src[2])) {
ce->ce_flags &= ~htons(CE_STAGEMASK);
src += 2;
nr -= 2;
active_nr -= 2;
}
*dst = ce;
src++;
dst++;
nr--;
}
}

int main(int argc, char **argv)
{
int i, newfd;
@ -85,19 +130,21 @@ int main(int argc, char **argv)
for (i = 1; i < argc; i++) {
const char *arg = argv[i];

/* "-m" stands for "merge" current directory cache */
/* "-m" stands for "merge", meaning we start in stage 1 */
if (!strcmp(arg, "-m")) {
if (active_cache)
die("read-tree: cannot merge old cache on top of new");
if (read_cache() < 0)
die("read-tree: corrupt directory cache");
stage = 1;
continue;
}
if (get_sha1_hex(arg, sha1) < 0)
usage("read-tree [-m] <sha1>");
if (stage > 3)
usage("can't merge more than two trees");
if (read_tree(sha1, "", 0) < 0)
die("failed to unpack tree object %s", arg);
stage++;
}
if (stage == 4)
trivially_merge_cache(active_cache, active_nr);
if (write_cache(newfd, active_cache, active_nr) ||
rename(".git/index.lock", ".git/index"))
die("unable to write new index file");