Am 30.09.19 um 23:10 schrieb Elijah Newren:
> If our input stream includes a tag which is later deleted, we were not
> properly deleting it.  We did have a step which would delete it, but we
> left a tag in the tag list noting that it needed to be updated, and the
> updating of annotated tags occurred AFTER ref deletion.  So, when we
> record that a tag needs to be deleted, also remove it from the list of
> annotated tags to update.
>
> While this has likely been something that has not happened in practice,
> it will come up more in order to support nested tags.  For nested tags,
> we either need to give temporary names to the intermediate tags and then
> delete them, or else we need to use the final name for the intermediate
> tags.  If we use the final name for the intermediate tags, then in order
> to keep the sanity check that someone doesn't try to update the same tag
> twice, we need to delete the ref after creating the intermediate tag.
> So, either way nested tags imply the need to delete temporary inner tag
> references.
>
> Signed-off-by: Elijah Newren <new...@gmail.com>
> ---
>  fast-import.c          | 29 +++++++++++++++++++++++++++++
>  t/t9300-fast-import.sh | 13 +++++++++++++
>  2 files changed, 42 insertions(+)
>
> diff --git a/fast-import.c b/fast-import.c
> index b44d6a467e..546da3a938 100644
> --- a/fast-import.c
> +++ b/fast-import.c
> @@ -2793,6 +2793,35 @@ static void parse_reset_branch(const char *arg)
>               b = new_branch(arg);
>       read_next_command();
>       parse_from(b);
> +     if (b->delete && !strncmp(b->name, "refs/tags/", 10)) {

b->name is a NUL-terminated string; starts_with() could be used to avoid
the magic number 10.

> +             /*
> +              * Elsewhere, we call dump_branches() before dump_tags(),
> +              * and dump_branches() will handle ref deletions first, so
> +              * in order to make sure the deletion actually takes effect,
> +              * we need to remove the tag from our list of tags to update.
> +              *
> +              * NEEDSWORK: replace list of tags with hashmap for faster
> +              * deletion?
> +              */
> +             struct strbuf tag_name = STRBUF_INIT;

This adds a small memory leak.

> +             struct tag *t, *prev = NULL;
> +             for (t = first_tag; t; t = t->next_tag) {
> +                     strbuf_reset(&tag_name);
> +                     strbuf_addf(&tag_name, "refs/tags/%s", t->name);
> +                     if (!strcmp(b->name, tag_name.buf))

So the strbuf is used to prefix t->name with "refs/tags/", which we know
b->name starts with, and to compare the result with b->name.  Removing
the "refs/tags/" prefix from b->name using skip_prefix() and comparing
the result with t->name would be easier.

> +                             break;
> +                     prev = t;
> +             }
> +             if (t) {
> +                     if (prev)
> +                             prev->next_tag = t->next_tag;
> +                     else
> +                             first_tag = t->next_tag;
> +                     if (!t->next_tag)
> +                             last_tag = prev;
> +                     /* There is no mem_pool_free(t) function to call. */
> +             }
> +     }
>       if (command_buf.len > 0)
>               unread_command_buf = 1;
>  }

Here's a squashable patch for that:

---
 fast-import.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/fast-import.c b/fast-import.c
index 70cd3f0ff4..a109591406 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -2779,6 +2779,7 @@ static void parse_new_tag(const char *arg)
 static void parse_reset_branch(const char *arg)
 {
        struct branch *b;
+       const char *tag_name;

        b = lookup_branch(arg);
        if (b) {
@@ -2794,7 +2795,7 @@ static void parse_reset_branch(const char *arg)
                b = new_branch(arg);
        read_next_command();
        parse_from(b);
-       if (b->delete && !strncmp(b->name, "refs/tags/", 10)) {
+       if (b->delete && skip_prefix(b->name, "refs/tags/", &tag_name)) {
                /*
                 * Elsewhere, we call dump_branches() before dump_tags(),
                 * and dump_branches() will handle ref deletions first, so
@@ -2804,12 +2805,9 @@ static void parse_reset_branch(const char *arg)
                 * NEEDSWORK: replace list of tags with hashmap for faster
                 * deletion?
                 */
-               struct strbuf tag_name = STRBUF_INIT;
                struct tag *t, *prev = NULL;
                for (t = first_tag; t; t = t->next_tag) {
-                       strbuf_reset(&tag_name);
-                       strbuf_addf(&tag_name, "refs/tags/%s", t->name);
-                       if (!strcmp(b->name, tag_name.buf))
+                       if (!strcmp(t->name, tag_name))
                                break;
                        prev = t;
                }
--
2.23.0

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