rebase -i: learn to rebase root commit

diff --git a/builtin-checkout.c b/builtin-checkout.c
index 57b94d282931187a0cb6394d4df707237038a7eb..c2c05613b67d7cc8bd3500bdbca4fc3533afaeee 100644 (file)
--- a/builtin-checkout.c
+++ b/builtin-checkout.c
@@ -47,7 +47,7 @@ static int post_checkout_hook(struct commit *old, struct commit *new,
 
        memset(&proc, 0, sizeof(proc));
        argv[0] = name;
-       argv[1] = xstrdup(sha1_to_hex(old->object.sha1));
+       argv[1] = xstrdup(sha1_to_hex(old ? old->object.sha1 : null_sha1));
        argv[2] = xstrdup(sha1_to_hex(new->object.sha1));
        argv[3] = changed ? "1" : "0";
        argv[4] = NULL;
@@ -228,7 +228,8 @@ static int checkout_paths(struct tree *source_tree, const char **pathspec,
        struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 
        newfd = hold_locked_index(lock_file, 1);
-       read_cache();
+       if (read_cache() < 0)
+               return error("corrupt index file");
 
        if (source_tree)
                read_tree_some(source_tree, pathspec);
@@ -371,7 +372,9 @@ static int merge_working_tree(struct checkout_opts *opts,
        int ret;
        struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
        int newfd = hold_locked_index(lock_file, 1);
-       read_cache();
+
+       if (read_cache() < 0)
+               return error("corrupt index file");
 
        if (opts->force) {
                ret = reset_tree(new->commit->tree, opts, 1);
@@ -397,8 +400,7 @@ static int merge_working_tree(struct checkout_opts *opts,
                }
 
                /* 2-way merge to the new branch */
-               topts.initial_checkout = (!active_nr &&
-                                         (old->commit == new->commit));
+               topts.initial_checkout = is_cache_unborn();
                topts.update = 1;
                topts.merge = 1;
                topts.gently = opts->merge;
@@ -492,10 +494,10 @@ static void update_refs_for_switch(struct checkout_opts *opts,
        }
 
        old_desc = old->name;
-       if (!old_desc)
+       if (!old_desc && old->commit)
                old_desc = sha1_to_hex(old->commit->object.sha1);
        strbuf_addf(&msg, "checkout: moving from %s to %s",
-                   old_desc, new->name);
+                   old_desc ? old_desc : "(invalid)", new->name);
 
        if (new->path) {
                create_symref("HEAD", new->path, msg.buf);
@@ -551,10 +553,10 @@ static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
         * a new commit, we want to mention the old commit once more
         * to remind the user that it might be lost.
         */
-       if (!opts->quiet && !old.path && new->commit != old.commit)
+       if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
                describe_detached_head("Previous HEAD position was", old.commit);
 
-       if (!old.commit) {
+       if (!old.commit && !opts->force) {
                if (!opts->quiet) {
                        fprintf(stderr, "warning: You appear to be on a branch yet to be born.\n");
                        fprintf(stderr, "warning: Forcing checkout of %s.\n", new->name);