[RFC PATCH] fast-export, fast-import: Let tags specify an internal name
- From
Luke Shumaker <lukeshu@lukeshu.com>
- Date
- Apr 20, 2021, 19:05 UTC
- Message-ID
- <20210420190552.822138-1-lukeshu@lukeshu.com>
From: Luke Shumaker <lukeshu@datawire.io>
A tag object contains the tag-name in the object, and is also pointed to by a ref named 'refs/tags/{tag-name}'. It's possible to end up with a tag for which the internal name and the refname disagree.
This "shouldn't" happen, but sometimes it can. In the "the coolest merge ever"[1], if Linus had wanted to import existing tags from Paul's gitk repo, he'd likely have wanted to give them a `gitk/` or `gitk-` prefix; you don't want gitk v0.0.1 to appear to be git v0.0.1, so when importing it, you'd rename the tag to `gitk/v0.0.1`.
(Less hypothetically, my employer's repo has _several_ such merges/imports, where the tags from each repo were given a prefix.)
That'd work fine if they're lightweight tags, but if they're annotated tags, then after the rename the internal name in the tag object (`v0.0.1`) is now different than the refname (`gitk/v0.0.1`). Which is still mostly fine, since not too many tools care if the internal name and the refname disagree.
But, fast-export/fast-import are tools that do care: it's currently impossible to represent these tags in a fast-import stream.
This patch adds an optional "name" sub-command to fast-import's "tag" top-level-command, the stream
tag foo
name bar
...will create a tag at "refs/tags/foo" that says "tag bar" internally.
These tags are things that "shouldn't" happen, so perhaps adding support for them to fast-export/fast-import is unwelcome, which is why I've marked this as an "RFC". If this addition is welcome, then it still needs tests and documentation.
[1]: https://lore.kernel.org/git/Pine.LNX.4.58.0506221433540.2353@ppc970.osdl.org/
--- Documentation/git-fast-import.txt | 1 + builtin/fast-export.c | 25 ++++++++++++++++++------- builtin/fast-import.c | 11 +++++++++-- 3 files changed, 28 insertions(+), 9 deletions(-)
diff --git a/Documentation/git-fast-import.txt b/Documentation/git-fast-import.txt index 39cfa05b28..6514b42d28 100644 --- a/Documentation/git-fast-import.txt +++ b/Documentation/git-fast-import.txt @@ -824,6 +824,7 @@ lightweight (non-annotated) tags see the `reset` command below. .... 'tag' SP <name> LF mark? + ('name' SP <name> LF)? 'from' SP <commit-ish> LF original-oid? 'tagger' (SP <name>)? SP LT <email> GT SP <when> LF diff --git a/builtin/fast-export.c b/builtin/fast-export.c index 85a76e0ef8..48e207a445 100644 --- a/builtin/fast-export.c +++ b/builtin/fast-export.c @@ -767,12 +767,13 @@ static void handle_tail(struct object_array *commits, struct rev_info *revs, } } -static void handle_tag(const char *name, struct tag *tag) +static void handle_tag(const char *refname, struct tag *tag) { unsigned long size; enum object_type type; char *buf; - const char *tagger, *tagger_end, *message; + const char *refbasename; + const char *tagname, *tagname_end, *tagger, *tagger_end, *message; size_t message_size = 0; struct object *tagged; int tagged_mark; @@ -800,6 +801,11 @@ static void handle_tag(const char *name, struct tag *tag) message += 2; message_size = strlen(message); } + tagname = memmem(buf, message ? message - buf : size, "\ntag ", 5); + if (!tagname) + die("malformed tag %s", oid_to_hex(&tag->object.oid)); + tagname += 5; + tagname_end = strchrnul(tagname, '\n'); tagger = memmem(buf, message ? message - buf : size, "\ntagger ", 8); if (!tagger) { if (fake_missing_tagger) @@ -816,7 +822,7 @@ static void handle_tag(const char *name, struct tag *tag) } if (anonymize) { - name = anonymize_refname(name); + refname = anonymize_refname(refname); if (message) { static struct hashmap tags; message = anonymize_str(&tags, anonymize_tag, @@ -870,7 +876,7 @@ static void handle_tag(const char *name, struct tag *tag) p = rewrite_commit((struct commit *)tagged); if (!p) { printf("reset %s\nfrom %s\n\n", - name, oid_to_hex(&null_oid)); + refname, oid_to_hex(&null_oid)); free(buf); return; } @@ -884,14 +890,19 @@ static void handle_tag(const char *name, struct tag *tag) if (tagged->type == OBJ_TAG) { printf("reset %s\nfrom %s\n\n", - name, oid_to_hex(&null_oid)); + refname, oid_to_hex(&null_oid)); } - skip_prefix(name, "refs/tags/", &name); - printf("tag %s\n", name); + refbasename = refname; + skip_prefix(refbasename, "refs/tags/", &refbasename); + printf("tag %s\n", refbasename); if (mark_tags) { mark_next_object(&tag->object); printf("mark :%"PRIu32"\n", last_idnum); } + if ((size_t)(tagname_end - tagname) != strlen(refbasename) || + strncmp(tagname, refbasename, (size_t)(tagname_end - tagname))) + printf("name %.*s\n", + (int)(tagname_end - tagname), tagname); if (tagged_mark) printf("from :%d\n", tagged_mark); else diff --git a/builtin/fast-import.c b/builtin/fast-import.c index 3afa81cf9a..24bdd46cba 100644 --- a/builtin/fast-import.c +++ b/builtin/fast-import.c @@ -2783,7 +2783,7 @@ static void parse_new_commit(const char *arg) static void parse_new_tag(const char *arg) { static struct strbuf msg = STRBUF_INIT; - const char *from; + const char *name, *from; char *tagger; struct branch *s; struct tag *t; @@ -2803,6 +2803,13 @@ static void parse_new_tag(const char *arg) read_next_command(); parse_mark(); + /* name ... */ + if (skip_prefix(command_buf.buf, "name ", &v)) { + name = strdupa(v); + read_next_command(); + } else + name = NULL; + /* from ... */ if (!skip_prefix(command_buf.buf, "from ", &from)) die("Expected from command, got %s", command_buf.buf); @@ -2850,7 +2857,7 @@ static void parse_new_tag(const char *arg) "object %s\n" "type %s\n" "tag %s\n", - oid_to_hex(&oid), type_name(type), t->name); + oid_to_hex(&oid), type_name(type), name ? name : t->name); if (tagger) strbuf_addf(&new_data, "tagger %s\n", tagger);
-- 2.31.1 Happy hacking, ~ Luke Shumaker