fsck-objects: refactor checking for connectivity

This separates the connectivity check into separate codepaths,
one for reachable objects and the other for unreachable ones,
while adding a lot of comments to explain what is going on.

When checking an unreachable object, unlike a reachable one, we
do not have to complain if it does not exist (we used to
complain about a missing blob even when the only thing that
references it is a tree that is dangling).  Also we do not have
to check and complain about objects that are referenced by an
unreachable object.

This makes the messages from fsck-objects a lot less noisy and
more useful.

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

diff --git a/fsck-objects.c b/fsck-objects.c
index 81f00db..ecfb014 100644 (file)
--- a/fsck-objects.c
+++ b/fsck-objects.c
@@ -54,6 +54,99 @@ static int objwarning(struct object *obj, const char *err, ...)
        return -1;
 }
 
+/*
+ * Check a single reachable object
+ */
+static void check_reachable_object(struct object *obj)
+{
+       const struct object_refs *refs;
+
+       /*
+        * We obviously want the object to be parsed,
+        * except if it was in a pack-file and we didn't
+        * do a full fsck
+        */
+       if (!obj->parsed) {
+               if (has_sha1_file(obj->sha1))
+                       return; /* it is in pack - forget about it */
+               printf("missing %s %s\n", typename(obj->type), sha1_to_hex(obj->sha1));
+               return;
+       }
+
+       /*
+        * Check that everything that we try to reference is also good.
+        */
+       refs = lookup_object_refs(obj);
+       if (refs) {
+               unsigned j;
+               for (j = 0; j < refs->count; j++) {
+                       struct object *ref = refs->ref[j];
+                       if (ref->parsed ||
+                           (has_sha1_file(ref->sha1)))
+                               continue;
+                       printf("broken link from %7s %s\n",
+                              typename(obj->type), sha1_to_hex(obj->sha1));
+                       printf("              to %7s %s\n",
+                              typename(ref->type), sha1_to_hex(ref->sha1));
+               }
+       }
+}
+
+/*
+ * Check a single unreachable object
+ */
+static void check_unreachable_object(struct object *obj)
+{
+       /*
+        * Missing unreachable object? Ignore it. It's not like
+        * we miss it (since it can't be reached), nor do we want
+        * to complain about it being unreachable (since it does
+        * not exist).
+        */
+       if (!obj->parsed)
+               return;
+
+       /*
+        * Unreachable object that exists? Show it if asked to,
+        * since this is something that is prunable.
+        */
+       if (show_unreachable) {
+               printf("unreachable %s %s\n", typename(obj->type), sha1_to_hex(obj->sha1));
+               return;
+       }
+
+       /*
+        * "!used" means that nothing at all points to it, including
+        * other unreacahble objects. In other words, it's the "tip"
+        * of some set of unreachable objects, usually a commit that
+        * got dropped.
+        *
+        * Such starting points are more interesting than some random
+        * set of unreachable objects, so we show them even if the user
+        * hasn't asked for _all_ unreachable objects. If you have
+        * deleted a branch by mistake, this is a prime candidate to
+        * start looking at, for example.
+        */
+       if (!obj->used) {
+               printf("dangling %s %s\n", typename(obj->type),
+                      sha1_to_hex(obj->sha1));
+               return;
+       }
+
+       /*
+        * Otherwise? It's there, it's unreachable, and some other unreachable
+        * object points to it. Ignore it - it's not interesting, and we showed
+        * all the interesting cases above.
+        */
+}
+
+static void check_object(struct object *obj)
+{
+       if (obj->flags & REACHABLE)
+               check_reachable_object(obj);
+       else
+               check_unreachable_object(obj);
+}
 
 static void check_connectivity(void)
 {
@@ -62,46 +155,10 @@ static void check_connectivity(void)
        /* Look up all the requirements, warn about missing objects.. */
        max = get_max_object_index();
        for (i = 0; i < max; i++) {
-               const struct object_refs *refs;
                struct object *obj = get_indexed_object(i);
 
-               if (!obj)
-                       continue;
-
-               if (!obj->parsed) {
-                       if (has_sha1_file(obj->sha1))
-                               ; /* it is in pack */
-                       else
-                               printf("missing %s %s\n",
-                                      typename(obj->type), sha1_to_hex(obj->sha1));
-                       continue;
-               }
-
-               refs = lookup_object_refs(obj);
-               if (refs) {
-                       unsigned j;
-                       for (j = 0; j < refs->count; j++) {
-                               struct object *ref = refs->ref[j];
-                               if (ref->parsed ||
-                                   (has_sha1_file(ref->sha1)))
-                                       continue;
-                               printf("broken link from %7s %s\n",
-                                      typename(obj->type), sha1_to_hex(obj->sha1));
-                               printf("              to %7s %s\n",
-                                      typename(ref->type), sha1_to_hex(ref->sha1));
-                       }
-               }
-
-               if (show_unreachable && !(obj->flags & REACHABLE)) {
-                       printf("unreachable %s %s\n",
-                              typename(obj->type), sha1_to_hex(obj->sha1));
-                       continue;
-               }
-
-               if (!obj->used) {
-                       printf("dangling %s %s\n", typename(obj->type),
-                              sha1_to_hex(obj->sha1));
-               }
+               if (obj)
+                       check_object(obj);
        }
 }