fast-import: prevent producing bad delta

[git.git] / fast-import.c

diff --git a/fast-import.c b/fast-import.c
index 78d978684da2e2b79340c138e1b6300100df1221..6dad9ff4db81bbdda0e44f2c59bb3dcc9f9fb585 100644 (file)
--- a/fast-import.c
+++ b/fast-import.c
@@ -170,6 +170,11 @@ Format of STDIN stream:
 #define DEPTH_BITS 13
 #define MAX_DEPTH ((1<<DEPTH_BITS)-1)
 
+/*
+ * We abuse the setuid bit on directories to mean "do not delta".
+ */
+#define NO_DELTA S_ISUID
+
 struct object_entry {
        struct pack_idx_entry idx;
        struct object_entry *next;
@@ -1414,8 +1419,9 @@ static void mktree(struct tree_content *t, int v, struct strbuf *b)
                struct tree_entry *e = t->entries[i];
                if (!e->versions[v].mode)
                        continue;
-               strbuf_addf(b, "%o %s%c", (unsigned int)e->versions[v].mode,
-                                       e->name->str_dat, '\0');
+               strbuf_addf(b, "%o %s%c",
+                       (unsigned int)(e->versions[v].mode & ~NO_DELTA),
+                       e->name->str_dat, '\0');
                strbuf_add(b, e->versions[v].sha1, 20);
        }
 }
@@ -1425,7 +1431,7 @@ static void store_tree(struct tree_entry *root)
        struct tree_content *t = root->tree;
        unsigned int i, j, del;
        struct last_object lo = { STRBUF_INIT, 0, 0, /* no_swap */ 1 };
-       struct object_entry *le;
+       struct object_entry *le = NULL;
 
        if (!is_null_sha1(root->versions[1].sha1))
                return;
@@ -1435,7 +1441,8 @@ static void store_tree(struct tree_entry *root)
                        store_tree(t->entries[i]);
        }
 
-       le = find_object(root->versions[0].sha1);
+       if (!(root->versions[0].mode & NO_DELTA))
+               le = find_object(root->versions[0].sha1);
        if (S_ISDIR(root->versions[0].mode) && le && le->pack_id == pack_id) {
                mktree(t, 0, &old_tree);
                lo.data = old_tree;
@@ -1469,6 +1476,7 @@ static void tree_content_replace(
 {
        if (!S_ISDIR(mode))
                die("Root cannot be a non-directory");
+       hashclr(root->versions[0].sha1);
        hashcpy(root->versions[1].sha1, sha1);
        if (root->tree)
                release_tree_content_recursive(root->tree);
@@ -1513,6 +1521,23 @@ static int tree_content_set(
                                if (e->tree)
                                        release_tree_content_recursive(e->tree);
                                e->tree = subtree;
+
+                               /*
+                                * We need to leave e->versions[0].sha1 alone
+                                * to avoid modifying the preimage tree used
+                                * when writing out the parent directory.
+                                * But after replacing the subdir with a
+                                * completely different one, it's not a good
+                                * delta base any more, and besides, we've
+                                * thrown away the tree entries needed to
+                                * make a delta against it.
+                                *
+                                * So let's just explicitly disable deltas
+                                * for the subtree.
+                                */
+                               if (S_ISDIR(e->versions[0].mode))
+                                       e->versions[0].mode |= NO_DELTA;
+
                                hashclr(root->versions[1].sha1);
                                return 1;
                        }
@@ -2927,7 +2952,7 @@ static void print_ls(int mode, const unsigned char *sha1, const char *path)
                /* mode SP type SP object_name TAB path LF */
                strbuf_reset(&line);
                strbuf_addf(&line, "%06o %s %s\t",
-                               mode, type, sha1_to_hex(sha1));
+                               mode & ~NO_DELTA, type, sha1_to_hex(sha1));
                quote_c_style(path, &line, NULL, 0);
                strbuf_addch(&line, '\n');
        }