diff options
author | Junio C Hamano <gitster@pobox.com> | 2018-02-14 21:18:55 +0300 |
---|---|---|
committer | Junio C Hamano <gitster@pobox.com> | 2018-02-16 22:22:43 +0300 |
commit | adcc94a0aa7055be4133ebda8b25f4af63285c6d (patch) | |
tree | 1411bcf159e21cf3fa6d6551d9aaa132025cdf62 /builtin | |
parent | b2e45c695d09f6a31ce09347ae0a5d2cdfe9dd4e (diff) |
merge: allow fast-forward when merging a tracked tag
Long time ago at fab47d05 ("merge: force edit and no-ff mode when
merging a tag object", 2011-11-07), "git merge" was made to always
create a merge commit when merging a tag, even when the side branch
being merged is a descendant of the current branch.
This default is good for merges made by upstream maintainers to
integrate work signed by downstream contributors, but will leave
pointless no-ff merges when downstream contributors pull a newer
release tag to make their long-running topic branches catch up with
the upstream. When there is no local work left on the topic, such a
merge should simply fast-forward to the commit pointed at by the
release tag.
Update the default (again) for "git merge" that merges a tag object
to (1) --no-ff (i.e. create a merge commit even when side branch
fast forwards) if the tag being merged is not at its expected place
in refs/tags/ hierarchy and (2) --ff (i.e. allow fast-forward update
when able) otherwise.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'builtin')
-rw-r--r-- | builtin/merge.c | 43 |
1 files changed, 39 insertions, 4 deletions
diff --git a/builtin/merge.c b/builtin/merge.c index 30264cfd7c..532522a854 100644 --- a/builtin/merge.c +++ b/builtin/merge.c @@ -33,6 +33,7 @@ #include "sequencer.h" #include "string-list.h" #include "packfile.h" +#include "tag.h" #define DEFAULT_TWOHEAD (1<<0) #define DEFAULT_OCTOPUS (1<<1) @@ -1125,6 +1126,43 @@ static struct commit_list *collect_parents(struct commit *head_commit, return remoteheads; } +static int merging_a_throwaway_tag(struct commit *commit) +{ + char *tag_ref; + struct object_id oid; + int is_throwaway_tag = 0; + + /* Are we merging a tag? */ + if (!merge_remote_util(commit) || + !merge_remote_util(commit)->obj || + merge_remote_util(commit)->obj->type != OBJ_TAG) + return is_throwaway_tag; + + /* + * Now we know we are merging a tag object. Are we downstream + * and following the tags from upstream? If so, we must have + * the tag object pointed at by "refs/tags/$T" where $T is the + * tagname recorded in the tag object. We want to allow such + * a "just to catch up" merge to fast-forward. + * + * Otherwise, we are playing an integrator's role, making a + * merge with a throw-away tag from a contributor with + * something like "git pull $contributor $signed_tag". + * We want to forbid such a merge from fast-forwarding + * by default; otherwise we would not keep the signature + * anywhere. + */ + tag_ref = xstrfmt("refs/tags/%s", + ((struct tag *)merge_remote_util(commit)->obj)->tag); + if (!read_ref(tag_ref, &oid) && + !oidcmp(&oid, &merge_remote_util(commit)->obj->oid)) + is_throwaway_tag = 0; + else + is_throwaway_tag = 1; + free(tag_ref); + return is_throwaway_tag; +} + int cmd_merge(int argc, const char **argv, const char *prefix) { struct object_id result_tree, stash, head_oid; @@ -1322,10 +1360,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix) oid_to_hex(&commit->object.oid)); setenv(buf.buf, merge_remote_util(commit)->name, 1); strbuf_reset(&buf); - if (fast_forward != FF_ONLY && - merge_remote_util(commit) && - merge_remote_util(commit)->obj && - merge_remote_util(commit)->obj->type == OBJ_TAG) + if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit)) fast_forward = FF_NO; } |