match-trees: use hashcpy to splice trees

When we splice trees together, we operate in place on the tree buffer.
If we're using SHA-1 for the hash algorithm, we may not have a full
GIT_MAX_RAWSZ (32) bytes to copy. Consequently, it doesn't logically
make sense for us to use a struct object_id to represent this type,
since it isn't a complete object.

Represent this value as a unsigned char pointer instead and copy it when
necessary.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/match-trees.c b/match-trees.c
index feca48a5fd2ab409e198266ac66ce71c49453af2..c2b7329e0988e27bd4c121212a9f8c1011295021 100644 (file)
--- a/match-trees.c
+++ b/match-trees.c
@@ -179,7 +179,7 @@ static int splice_tree(const struct object_id *oid1, const char *prefix,
        char *buf;
        unsigned long sz;
        struct tree_desc desc;
-       struct object_id *rewrite_here;
+       unsigned char *rewrite_here;
        const struct object_id *rewrite_with;
        struct object_id subtree;
        enum object_type type;
@@ -206,9 +206,19 @@ static int splice_tree(const struct object_id *oid1, const char *prefix,
                        if (!S_ISDIR(mode))
                                die("entry %s in tree %s is not a tree", name,
                                    oid_to_hex(oid1));
-                       rewrite_here = (struct object_id *)(desc.entry.path +
-                                                           strlen(desc.entry.path) +
-                                                           1);
+
+                       /*
+                        * 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);
@@ -217,14 +227,16 @@ static int splice_tree(const struct object_id *oid1, const char *prefix,
                die("entry %.*s not found in tree %s", toplen, prefix,
                    oid_to_hex(oid1));
        if (*subpath) {
-               status = splice_tree(rewrite_here, subpath, oid2, &subtree);
+               struct object_id tree_oid;
+               hashcpy(tree_oid.hash, rewrite_here);
+               status = splice_tree(&tree_oid, subpath, oid2, &subtree);
                if (status)
                        return status;
                rewrite_with = &subtree;
        } else {
                rewrite_with = oid2;
        }
-       oidcpy(rewrite_here, rewrite_with);
+       hashcpy(rewrite_here, rewrite_with->hash);
        status = write_object_file(buf, sz, tree_type, result);
        free(buf);
        return status;