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git/match-trees.c

365 lines
8.5 KiB

#include "cache.h"
#include "tree.h"
#include "tree-walk.h"
#include "object-store.h"
static int score_missing(unsigned mode)
{
int score;
if (S_ISDIR(mode))
score = -1000;
else if (S_ISLNK(mode))
score = -500;
else
score = -50;
return score;
}
static int score_differs(unsigned mode1, unsigned mode2)
{
int score;
if (S_ISDIR(mode1) != S_ISDIR(mode2))
score = -100;
else if (S_ISLNK(mode1) != S_ISLNK(mode2))
score = -50;
else
score = -5;
return score;
}
static int score_matches(unsigned mode1, unsigned mode2)
{
int score;
/* Heh, we found SHA-1 collisions between different kind of objects */
if (S_ISDIR(mode1) != S_ISDIR(mode2))
score = -100;
else if (S_ISLNK(mode1) != S_ISLNK(mode2))
score = -50;
else if (S_ISDIR(mode1))
score = 1000;
else if (S_ISLNK(mode1))
score = 500;
else
score = 250;
return score;
}
static void *fill_tree_desc_strict(struct tree_desc *desc,
const struct object_id *hash)
{
void *buffer;
enum object_type type;
unsigned long size;
buffer = read_object_file(hash, &type, &size);
if (!buffer)
die("unable to read tree (%s)", oid_to_hex(hash));
if (type != OBJ_TREE)
die("%s is not a tree", oid_to_hex(hash));
init_tree_desc(desc, buffer, size);
return buffer;
}
static int base_name_entries_compare(const struct name_entry *a,
const struct name_entry *b)
{
return base_name_compare(a->path, tree_entry_len(a), a->mode,
b->path, tree_entry_len(b), b->mode);
}
/*
* Inspect two trees, and give a score that tells how similar they are.
*/
static int score_trees(const struct object_id *hash1, const struct object_id *hash2)
{
struct tree_desc one;
struct tree_desc two;
void *one_buf = fill_tree_desc_strict(&one, hash1);
void *two_buf = fill_tree_desc_strict(&two, hash2);
int score = 0;
for (;;) {
int cmp;
if (one.size && two.size)
cmp = base_name_entries_compare(&one.entry, &two.entry);
else if (one.size)
/* two lacks this entry */
cmp = -1;
else if (two.size)
/* two has more entries */
cmp = 1;
else
break;
if (cmp < 0) {
/* path1 does not appear in two */
score += score_missing(one.entry.mode);
update_tree_entry(&one);
} else if (cmp > 0) {
/* path2 does not appear in one */
score += score_missing(two.entry.mode);
update_tree_entry(&two);
} else {
/* path appears in both */
if (!oideq(&one.entry.oid, &two.entry.oid)) {
/* they are different */
score += score_differs(one.entry.mode,
two.entry.mode);
} else {
/* same subtree or blob */
score += score_matches(one.entry.mode,
two.entry.mode);
}
update_tree_entry(&one);
update_tree_entry(&two);
}
}
free(one_buf);
free(two_buf);
return score;
}
/*
* Match one itself and its subtrees with two and pick the best match.
*/
static void match_trees(const struct object_id *hash1,
const struct object_id *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 struct object_id *elem;
unsigned short 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) {
free(*best_match);
*best_match = xstrfmt("%s%s", base, path);
*best_score = score;
}
if (recurse_limit) {
char *newbase = xstrfmt("%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);
}
/*
* A tree "oid1" has a subdirectory at "prefix". Come up with a tree object by
* replacing it with another tree "oid2".
*/
static int splice_tree(const struct object_id *oid1, const char *prefix,
const struct object_id *oid2, struct object_id *result)
{
char *subpath;
int toplen;
char *buf;
unsigned long sz;
struct tree_desc desc;
unsigned char *rewrite_here;
const struct object_id *rewrite_with;
struct object_id subtree;
enum object_type type;
int status;
subpath = strchrnul(prefix, '/');
toplen = subpath - prefix;
if (*subpath)
subpath++;
buf = read_object_file(oid1, &type, &sz);
if (!buf)
die("cannot read tree %s", oid_to_hex(oid1));
init_tree_desc(&desc, buf, sz);
rewrite_here = NULL;
while (desc.size) {
const char *name;
unsigned short mode;
tree_entry_extract(&desc, &name, &mode);
if (strlen(name) == toplen &&
!memcmp(name, prefix, toplen)) {
if (!S_ISDIR(mode))
die("entry %s in tree %s is not a tree", name,
oid_to_hex(oid1));
/*
* We cast here for two reasons:
*
* - to flip the "char *" (for the path) to "unsigned
* char *" (for the hash stored after it)
*
* - to discard the "const"; this is OK because we
* know it points into our non-const "buf"
*/
rewrite_here = (unsigned char *)(desc.entry.path +
strlen(desc.entry.path) +
1);
break;
}
update_tree_entry(&desc);
}
if (!rewrite_here)
die("entry %.*s not found in tree %s", toplen, prefix,
oid_to_hex(oid1));
if (*subpath) {
struct object_id tree_oid;
oidread(&tree_oid, rewrite_here);
status = splice_tree(&tree_oid, subpath, oid2, &subtree);
if (status)
return status;
rewrite_with = &subtree;
} else {
rewrite_with = oid2;
}
hashcpy(rewrite_here, rewrite_with->hash);
status = write_object_file(buf, sz, OBJ_TREE, result);
free(buf);
return status;
}
/*
* 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(struct repository *r,
const struct object_id *hash1,
const struct object_id *hash2,
struct object_id *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 */
oidcpy(shifted, hash2);
if (add_score < del_score) {
/* We need to pick a subtree of two */
unsigned short mode;
if (!*del_prefix)
return;
if (get_tree_entry(r, hash2, del_prefix, shifted, &mode))
die("cannot find path %s in tree %s",
del_prefix, oid_to_hex(hash2));
return;
}
if (!*add_prefix)
return;
splice_tree(hash1, add_prefix, hash2, shifted);
}
/*
* 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(struct repository *r,
const struct object_id *hash1,
const struct object_id *hash2,
struct object_id *shifted,
const char *shift_prefix)
{
struct object_id sub1, sub2;
unsigned short mode1, mode2;
unsigned candidate = 0;
/* Can hash2 be a tree at shift_prefix in tree hash1? */
if (!get_tree_entry(r, 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(r, 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 */
oidcpy(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.
*/
oidcpy(shifted, &sub2);
}