From: Eric Sunshine <sunshine@sunshineco.com>
Date: Sun, 22 Mar 2026 02:04:01 GMT
Subject: Re: [GSoC PATCH 2/3] pack-write: add helper to fill promisor file after repack
Message-ID: <CAPig+cQSsMfvHJnwuXGQ1Je8ekz=Rqbaibn-3shbya5y-5xTKg@mail.gmail.com>
In-Reply-To: <3c0702f81b3e4a57cd38284ab90f8277da3fcd40.1774125871.git.lorenzo.pegorari2002@gmail.com>

On Sat, Mar 21, 2026 at 5:29 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. A better way to achieve this might be (is
> definitely) possible.
>
> Signed-off-by: LorenzoPegorari <lorenzo.pegorari2002@gmail.com>
> ---
> diff --git a/pack-write.c b/pack-write.c
> @@ -621,3 +621,65 @@ 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 strbuf promisor_source_name = STRBUF_INIT;
> +       struct strbuf read_source = STRBUF_INIT, read_dest = STRBUF_INIT;
> +       struct strbuf write_dest = STRBUF_INIT;

These strbufs don't seem to be released, thus are leaked.

> +       int err;
> +
> +       FILE *dest = xfopen(promisor_name, "r+");
> +
> +       struct packed_git *p;

Style nit: Place all the variable declarations together (without blank
lines), followed by a blank line.

> +       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");
> +               FILE *source = xfopen(promisor_source_name.buf, "r");

This project still frowns upon variable declaration after code. You
will want to declare `FILE *source;` at the top of this loop body and
then assign `source = xfopen(...)` here.

> +               /*
> +                * 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_source, source) != EOF) {
> +                       if (fseek(dest, 0L, SEEK_SET))
> +                               die_errno(_("fseek failed"));
> +                       int is_source_in_dest = 0;

Ditto regarding variable declaration following code.

> +                       while (strbuf_getline(&read_dest, dest) != EOF) {
> +                               if (!strbuf_cmp(&read_source, &read_dest)) {
> +                                       is_source_in_dest = 1;
> +                                       break;
> +                               }
> +                       }
> +                       if (!is_source_in_dest) {
> +                               strbuf_addbuf(&write_dest, &read_source);
> +                               strbuf_addstr(&write_dest, "\n");
> +                       }

The commit message talks about this, and it is indeed very ugly that
this re-reads `dest` from the beginning for *every* `source` line. Is
there a reason you can't simply read `dest` into a `strset` (see Git's
`strmap.h`) in its entirety before entering the repo_for_each_pack()
loop and then merely check the strset for existence using
strset_add()?

> +               }
> +
> +               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);
> +                       fflush(dest);
> +                       strbuf_reset(&write_dest);
> +               }
> +
> +               err = ferror(source);
> +               err |= fclose(source);
> +               if (err)
> +                       die(_("could not read '%s' promisor file"), promisor_source_name.buf);
> +       }
> +
> +       err = ferror(dest);
> +       err |= fclose(dest);
> +       if (err)
> +               die(_("could not write '%s' promisor file"), promisor_name);
> +}