From: Eric Sunshine <sunshine@sunshineco.com>
Date: Mon, 23 Mar 2026 20:27:44 GMT
Subject: Re: [GSoC PATCH v2 2/4] pack-write: add helper to fill promisor file after repack
Message-ID: <CAPig+cR7-3rdkHvGbzk8O7P=83pxBTvqXTUgMxYpf+OK9jNCgg@mail.gmail.com>
In-Reply-To: <0bb031e7443bb53abbbb0afaa347285d6d8cf7b8.1774205661.git.lorenzo.pegorari2002@gmail.com>

On Sun, Mar 22, 2026 at 3:18 PM LorenzoPegorari
<lorenzo.pegorari2002@gmail.com> wrote:
> Create a `copy_all_promisor_files()` helper function used to copy the
> contents of all ".promisor" files in a `repository` inside another
> ".promisor" file.
>
> This function can be used to preserve the contents of all ".promisor"
> files inside a new ".promisor" file, for example when a repack happens.
>
> This function is written in such a way so that it will read all the
> ".promisor" files inside the given `repository` line by line, and copy
> only the lines that are not already present in the destination file. This
> is done to avoid copying the same lines multiple times that may come from
> multiple (redundant) packfiles. There might be another better/cleaner way
> to achieve this.
>
> Signed-off-by: LorenzoPegorari <lorenzo.pegorari2002@gmail.com>
> ---

Thanks, I think this version addresses all my review comments[*] and
looks much better overall. Use of `strset` makes a big difference over
the previous attempt. A couple minor comments below...

[*]: https://lore.kernel.org/git/CAPig+cQSsMfvHJnwuXGQ1Je8ekz=Rqbaibn-3shbya5y-5xTKg@mail.gmail.com/

> diff --git a/pack-write.c b/pack-write.c
> @@ -621,3 +622,63 @@ void write_promisor_file(const char *promisor_name, struct ref **sought, int nr_
> +void copy_all_promisor_files(struct repository *repo, const char *promisor_name)
> +{
> +       struct strset dest_content = STRSET_INIT;
> +       struct strbuf read_line = STRBUF_INIT;
> +       struct strbuf promisor_source_name = STRBUF_INIT;
> +       struct strbuf write_dest = STRBUF_INIT;
> +       FILE *dest, *source;
> +       struct packed_git *p;
> +       int err;

Nit: I probably would have declared `FILE *dest` within the scope of
the repo_for_each_pack() loop as suggested in the review, but it's not
worth a reroll.

> +       dest = xfopen(promisor_name, "r+");
> +       while (strbuf_getline(&read_line, dest) != EOF)
> +               strset_add(&dest_content, read_line.buf);
> +
> +       repo_for_each_pack(repo, p) {
> +               if (!p->pack_promisor)
> +                       continue;
> +
> +               strbuf_reset(&promisor_source_name);
> +               strbuf_addstr(&promisor_source_name, p->pack_name);
> +               strbuf_strip_suffix(&promisor_source_name, ".pack");
> +               strbuf_addstr(&promisor_source_name, ".promisor");
> +               source = xfopen(promisor_source_name.buf, "r");
> +
> +               /*
> +                * For each line of the promisor source file, check if it already
> +                * is in the promisor dest file. If not, add it to write_dest, so
> +                * that it will be written in the dest file.
> +                */
> +               while (strbuf_getline(&read_line, source) != EOF) {
> +                       if (strset_add(&dest_content, read_line.buf)) {
> +                               strbuf_addbuf(&write_dest, &read_line);
> +                               strbuf_addstr(&write_dest, "\n");

Not worth a reroll, but this could also be:

    strbuf_addch(&write_dest, '\n');

> +                       }
> +               }
> +
> +               err = ferror(source);
> +               err |= fclose(source);
> +               if (err)
> +                       die(_("could not read '%s' promisor file"), promisor_source_name.buf);
> +       }
> +
> +       if (write_dest.len) {
> +               strbuf_strip_suffix(&write_dest, "\n");
> +               if (fseek(dest, 0L, SEEK_END))
> +                       die_errno(_("fseek failed"));
> +               fprintf(dest, "%s\n", write_dest.buf);
> +       }

Can you explain why you strip "\n" and then re-add it via fprintf()?
The reason is not immediately obvious.

> +       err = ferror(dest);
> +       err |= fclose(dest);
> +       if (err)
> +               die(_("could not write '%s' promisor file"), promisor_name);
> +
> +       strbuf_release(&read_line);
> +       strbuf_release(&promisor_source_name);
> +       strbuf_release(&write_dest);
> +       strset_clear(&dest_content);
> +}

Everything appears to be released. Good.