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/*
* GIT - The information manager from hell
*
* Copyright (C) Linus Torvalds, 2005
*/
#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);
unsigned int size = cache_entry_size(baselen + len);
struct cache_entry *ce = malloc(size);
memset(ce, 0, size);
ce->ce_mode = htonl(mode);
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);
return add_cache_entry(ce, 1);
}
static int read_tree(unsigned char *sha1, const char *base, int baselen)
{
void *buffer;
unsigned long size;
char type[20];
buffer = read_sha1_file(sha1, type, &size);
if (!buffer)
return -1;
if (strcmp(type, "tree"))
return -1;
while (size) {
int len = strlen(buffer)+1;
unsigned char *sha1 = buffer + len;
char *path = strchr(buffer, ' ')+1;
unsigned int mode;
if (size < len + 20 || sscanf(buffer, "%o", &mode) != 1)
return -1;
buffer = sha1 + 20;
size -= len + 20;
if (S_ISDIR(mode)) {
int retval;
int pathlen = strlen(path);
char *newbase = malloc(baselen + 1 + pathlen);
memcpy(newbase, base, baselen);
memcpy(newbase + baselen, path, pathlen);
newbase[baselen + pathlen] = '/';
retval = read_tree(sha1, newbase, baselen + pathlen + 1);
free(newbase);
if (retval)
return -1;
continue;
}
if (read_one_entry(sha1, base, baselen, path, mode) < 0)
return -1;
}
return 0;
}
static int remove_lock = 0;
static void remove_lock_file(void)
{
if (remove_lock)
unlink(".git/index.lock");
}
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)
{
struct cache_entry **dst = src;
while (nr) {
struct cache_entry *ce, *result;
ce = src[0];
if (nr > 2 && (result = merge_entries(ce, src[1], src[2])) != NULL) {
ce = result;
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;
unsigned char sha1[20];
newfd = open(".git/index.lock", O_RDWR | O_CREAT | O_EXCL, 0600);
if (newfd < 0)
die("unable to create new cachefile");
atexit(remove_lock_file);
remove_lock = 1;
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")) {
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");
remove_lock = 0;
return 0;
}
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