summaryrefslogtreecommitdiff
path: root/match-trees.c
diff options
context:
space:
mode:
Diffstat (limited to 'match-trees.c')
-rw-r--r--match-trees.c69
1 files changed, 68 insertions, 1 deletions
diff --git a/match-trees.c b/match-trees.c
index 0fd6df7d6e..26f7ed143e 100644
--- a/match-trees.c
+++ b/match-trees.c
@@ -185,7 +185,7 @@ static void match_trees(const unsigned char *hash1,
* tree object by replacing it with another tree "hash2".
*/
static int splice_tree(const unsigned char *hash1,
- char *prefix,
+ const char *prefix,
const unsigned char *hash2,
unsigned char *result)
{
@@ -264,6 +264,13 @@ void shift_tree(const unsigned char *hash1,
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);
@@ -301,3 +308,63 @@ void shift_tree(const unsigned char *hash1,
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(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);
+}