checkout -m: no need to insist on having all 3 stages

The content level merge machinery ll_merge() is prepared to merge
correctly in "both sides added differently" case by using an empty blob as
if it were the common ancestor. "checkout -m" could do the same, but didn't
bother supporting it and instead insisted on having all three stages.

Reported-by: Pete Harlan
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/checkout.c b/builtin/checkout.c
index eece5d6ac0f48ae76dc76c0f2ebda633cc0ded58..31aa248c0e8f2bdba8a6c666dd8a4c2a62b63c3f 100644 (file)
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -110,16 +110,21 @@ static int check_stage(int stage, struct cache_entry *ce, int pos)
                return error(_("path '%s' does not have their version"), ce->name);
 }
 
-static int check_all_stages(struct cache_entry *ce, int pos)
+static int check_stages(unsigned stages, struct cache_entry *ce, int pos)
 {
-       if (ce_stage(ce) != 1 ||
-           active_nr <= pos + 2 ||
-           strcmp(active_cache[pos+1]->name, ce->name) ||
-           ce_stage(active_cache[pos+1]) != 2 ||
-           strcmp(active_cache[pos+2]->name, ce->name) ||
-           ce_stage(active_cache[pos+2]) != 3)
-               return error(_("path '%s' does not have all three versions"),
-                            ce->name);
+       unsigned seen = 0;
+       const char *name = ce->name;
+
+       while (pos < active_nr) {
+               ce = active_cache[pos];
+               if (strcmp(name, ce->name))
+                       break;
+               seen |= (1 << ce_stage(ce));
+               pos++;
+       }
+       if ((stages & seen) != stages)
+               return error(_("path '%s' does not have all necessary versions"),
+                            name);
        return 0;
 }
 
@@ -146,18 +151,27 @@ static int checkout_merged(int pos, struct checkout *state)
        int status;
        unsigned char sha1[20];
        mmbuffer_t result_buf;
+       unsigned char threeway[3][20];
+       unsigned mode;
+
+       memset(threeway, 0, sizeof(threeway));
+       while (pos < active_nr) {
+               int stage;
+               stage = ce_stage(ce);
+               if (!stage || strcmp(path, ce->name))
+                       break;
+               hashcpy(threeway[stage - 1], ce->sha1);
+               if (stage == 2)
+                       mode = create_ce_mode(ce->ce_mode);
+               pos++;
+               ce = active_cache[pos];
+       }
+       if (is_null_sha1(threeway[1]) || is_null_sha1(threeway[2]))
+               return error(_("path '%s' does not have necessary versions"), path);
 
-       if (ce_stage(ce) != 1 ||
-           active_nr <= pos + 2 ||
-           strcmp(active_cache[pos+1]->name, path) ||
-           ce_stage(active_cache[pos+1]) != 2 ||
-           strcmp(active_cache[pos+2]->name, path) ||
-           ce_stage(active_cache[pos+2]) != 3)
-               return error(_("path '%s' does not have all 3 versions"), path);
-
-       read_mmblob(&ancestor, active_cache[pos]->sha1);
-       read_mmblob(&ours, active_cache[pos+1]->sha1);
-       read_mmblob(&theirs, active_cache[pos+2]->sha1);
+       read_mmblob(&ancestor, threeway[0]);
+       read_mmblob(&ours, threeway[1]);
+       read_mmblob(&theirs, threeway[2]);
 
        /*
         * NEEDSWORK: re-create conflicts from merges with
@@ -188,9 +202,7 @@ static int checkout_merged(int pos, struct checkout *state)
        if (write_sha1_file(result_buf.ptr, result_buf.size,
                            blob_type, sha1))
                die(_("Unable to add merge result for '%s'"), path);
-       ce = make_cache_entry(create_ce_mode(active_cache[pos+1]->ce_mode),
-                             sha1,
-                             path, 2, 0);
+       ce = make_cache_entry(mode, sha1, path, 2, 0);
        if (!ce)
                die(_("make_cache_entry failed for path '%s'"), path);
        status = checkout_entry(ce, state, NULL);
@@ -246,7 +258,7 @@ static int checkout_paths(struct tree *source_tree, const char **pathspec,
                        } else if (stage) {
                                errs |= check_stage(stage, ce, pos);
                        } else if (opts->merge) {
-                               errs |= check_all_stages(ce, pos);
+                               errs |= check_stages((1<<2) | (1<<3), ce, pos);
                        } else {
                                errs = 1;
                                error(_("path '%s' is unmerged"), ce->name);