[PATCH] Accept commit in some places when tree is needed.

This patch implements read_tree_with_tree_or_commit_sha1(),
which can be used when you are interested in reading an unpacked
raw tree data but you do not know nor care if the SHA1 you
obtained your user is a tree ID or a commit ID.  Before this
function's introduction, you would have called read_sha1_file(),
examined its type, parsed it to call read_sha1_file() again if
it is a commit, and verified that the resulting object is a
tree.  Instead, this function does that for you.  It returns
NULL if the given SHA1 is not either a tree or a commit.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/cache.h b/cache.h
index a67b79e..378299a 100644 (file)
--- a/cache.h
+++ b/cache.h
@@ -125,4 +125,8 @@ extern int error(const char *err, ...);
 
 extern int cache_name_compare(const char *name1, int len1, const char *name2, int len2);
 
+extern void *read_tree_with_tree_or_commit_sha1(const unsigned char *sha1,
+                                               unsigned long *size,
+                                               unsigned char *tree_sha1_ret);
+
 #endif /* CACHE_H */

diff --git a/sha1_file.c b/sha1_file.c
index eee3598..7b7b65d 100644 (file)
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -166,6 +166,46 @@ void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size
        return NULL;
 }
 
+void *read_tree_with_tree_or_commit_sha1(const unsigned char *sha1,
+                                        unsigned long *size,
+                                        unsigned char *tree_sha1_return)
+{
+       char type[20];
+       void *buffer;
+       unsigned long isize;
+       int was_commit = 0;
+       char tree_sha1[20];
+
+       buffer = read_sha1_file(sha1, type, &isize);
+
+       /* 
+        * We might have read a commit instead of a tree, in which case
+        * we parse out the tree_sha1 and attempt to read from there.
+        * (buffer + 5) is because the tree sha1 is always at offset 5
+        * in a commit record ("tree ").
+        */
+       if (buffer &&
+           !strcmp(type, "commit") &&
+           !get_sha1_hex(buffer + 5, tree_sha1)) {
+               free(buffer);
+               buffer = read_sha1_file(tree_sha1, type, &isize);
+               was_commit = 1;
+       }
+
+       /*
+        * Now do we have something and if so is it a tree?
+        */
+       if (!buffer || strcmp(type, "tree")) {
+               free(buffer);
+               return;
+       }
+
+       *size = isize;
+       if (tree_sha1_return)
+               memcpy(tree_sha1_return, was_commit ? tree_sha1 : sha1, 20);
+       return buffer;
+}
+
 int write_sha1_file(char *buf, unsigned len, unsigned char *returnsha1)
 {
        int size;