git log -p -m: document -m and honor --first-parent

diff --git a/match-trees.c b/match-trees.c
index 0fd6df7d6ed839eaed536bc332312c2688a6bbad..26f7ed143e0649b6377ea427b5c57ca7ddb663d3 100644 (file)
--- 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);
+}