/*
* The user says the trees will be shifted by this much.
* Unfortunately we cannot fundamentally tell which one to
* be prefixed, as recursive merge can work in either direction.
*/
void shift_tree_by(const unsigned char *hash1,
const unsigned char *hash2,
unsigned char *shifted,
const char *shift_prefix)
{
unsigned char sub1[20], sub2[20];
unsigned mode1, mode2;
unsigned candidate = 0;
/* Can hash2 be a tree at shift_prefix in tree hash1? */
if (!get_tree_entry(hash1, shift_prefix, sub1, &mode1) &&
S_ISDIR(mode1))
candidate |= 1;
/* Can hash1 be a tree at shift_prefix in tree hash2? */
if (!get_tree_entry(hash2, shift_prefix, sub2, &mode2) &&
S_ISDIR(mode2))
candidate |= 2;
if (candidate == 3) {
/* Both are plausible -- we need to evaluate the score */
int best_score = score_trees(hash1, hash2);
int score;
candidate = 0;
score = score_trees(sub1, hash2);
if (score > best_score) {
candidate = 1;
best_score = score;
}
score = score_trees(sub2, hash1);
if (score > best_score)
candidate = 2;
}
if (!candidate) {
/* Neither is plausible -- do not shift */
hashcpy(shifted, hash2);
return;
}
if (candidate == 1)
/*
* shift tree2 down by adding shift_prefix above it
* to match tree1.
*/
splice_tree(hash1, shift_prefix, hash2, shifted);
else
/*
* shift tree2 up by removing shift_prefix from it
* to match tree1.
*/
hashcpy(shifted, sub2);
}
/*
* We are trying to come up with a merge between one and two that
* results in a tree shape similar to one. The tree two might
* correspond to a subtree of one, in which case it needs to be
* shifted down by prefixing otherwise empty directories. On the
* other hand, it could cover tree one and we might need to pick a
* subtree of it.
*/
void shift_tree(const unsigned char *hash1,
const unsigned char *hash2,
unsigned char *shifted,
int depth_limit)
{
char *add_prefix;
char *del_prefix;
int add_score, del_score;
/*
* NEEDSWORK: this limits the recursion depth to hardcoded
* value '2' to avoid excessive overhead.
*/
if (!depth_limit)
depth_limit = 2;
add_score = del_score = score_trees(hash1, hash2);
add_prefix = xcalloc(1, 1);
del_prefix = xcalloc(1, 1);
/*
* See if one's subtree resembles two; if so we need to prefix
* two with a few fake trees to match the prefix.
*/
match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit);
/*
* See if two's subtree resembles one; if so we need to
* pick only subtree of two.
*/
match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit);
/* Assume we do not have to do any shifting */
hashcpy(shifted, hash2);
if (add_score < del_score) {
/* We need to pick a subtree of two */
unsigned mode;
if (!*del_prefix)
return;
if (get_tree_entry(hash2, del_prefix, shifted, &mode))
die("cannot find path %s in tree %s",
del_prefix, sha1_to_hex(hash2));
return;
}
if (!*add_prefix)
return;
splice_tree(hash1, add_prefix, hash2, shifted);
}
/*
* Match one itself and its subtrees with two and pick the best match.
*/
static void match_trees(const unsigned char *hash1,
const unsigned char *hash2,
int *best_score,
char **best_match,
const char *base,
int recurse_limit)
{
struct tree_desc one;
void *one_buf;
enum object_type type;
unsigned long size;
one_buf = read_sha1_file(hash1, &type, &size);
if (!one_buf)
die("unable to read tree (%s)", sha1_to_hex(hash1));
if (type != OBJ_TREE)
die("%s is not a tree", sha1_to_hex(hash1));
init_tree_desc(&one, one_buf, size);
while (one.size) {
const char *path;
const unsigned char *elem;
unsigned mode;
int score;
elem = tree_entry_extract(&one, &path, &mode);
if (!S_ISDIR(mode))
goto next;
score = score_trees(elem, hash2);
if (*best_score < score) {
char *newpath;
newpath = xmalloc(strlen(base) + strlen(path) + 1);
sprintf(newpath, "%s%s", base, path);
free(*best_match);
*best_match = newpath;
*best_score = score;
}
if (recurse_limit) {
char *newbase;
newbase = xmalloc(strlen(base) + strlen(path) + 2);
sprintf(newbase, "%s%s/", base, path);
match_trees(elem, hash2, best_score, best_match,
newbase, recurse_limit - 1);
free(newbase);
}
next:
update_tree_entry(&one);
}
free(one_buf);
}
/*
* Match one itself and its subtrees with two and pick the best match.
*/
static void match_trees(const unsigned char *hash1,
const unsigned char *hash2,
int *best_score,
char **best_match,
const char *base,
int recurse_limit)
{
struct tree_desc one;
void *one_buf = fill_tree_desc_strict(&one, hash1);
while (one.size) {
const char *path;
const unsigned char *elem;
unsigned mode;
int score;
elem = tree_entry_extract(&one, &path, &mode);
if (!S_ISDIR(mode))
goto next;
score = score_trees(elem, hash2);
if (*best_score < score) {
char *newpath;
newpath = xmalloc(strlen(base) + strlen(path) + 1);
sprintf(newpath, "%s%s", base, path);
free(*best_match);
*best_match = newpath;
*best_score = score;
}
if (recurse_limit) {
char *newbase;
newbase = xmalloc(strlen(base) + strlen(path) + 2);
sprintf(newbase, "%s%s/", base, path);
match_trees(elem, hash2, best_score, best_match,
newbase, recurse_limit - 1);
free(newbase);
}
next:
update_tree_entry(&one);
}
free(one_buf);
}
