[GSoC PATCH v6 2/6] repack-promisor add helper to fill promisor file after repack

From

LorenzoPegorari <lorenzo.pegorari2002@gmail.com>

Date

Apr 18, 2026, 14:17 UTC

Message-ID

<de28baad3839f5c6e74352eae4de7763124e7fb8.1776384902.git.lorenzo.pegorari2002@gmail.com>

In-Reply-To

<cover.1776384902.git.lorenzo.pegorari2002@gmail.com>

The function logic is the following:
 * Take all ".promisor" files contained inside the given `repo`.
 * Ignore those whose name is contained inside the given `strset
   not_repacked_names`, which basically acts as a "promisor ignorelist"
   (intended to be used for packfiles that have not been repacked).
 * Read each line of the remaining ".promisor" files, which can be:
    * "<oid> <ref>" if the ".promisor" file was never repacked. If so,
      add the time (in Unix time) at which the ".promisor" file was last
      modified <time> to the line, to obtain: "<oid> <ref> <time>".
    * "<oid> <ref> <time>" if the ".promisor" file was repacked. If so,
      don't modify it.
 * Ignore the line if its <oid> is not present inside the
   "<packtmp>-<dest_hex>.idx" file.
 * If the destination file "<packtmp>-<dest_hex>.promisor" does not
   already contain the line, append it to the file.

The function tries its best to deal with malformed ".promisor" files,
ignoring those lines:
 * That cannot be split into "<oid> <ref>" or "<oid> <ref> <time>".
 * Whose <oid> is not a sane hexadecimal string.
 * Whose <ref> does not have the correct format for a refname.

Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Helped-by: Tian Yuchen <cat@malon.dev>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: LorenzoPegorari <lorenzo.pegorari2002@gmail.com>
---
 repack-promisor.c | 149 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 149 insertions(+)

diff --git a/repack-promisor.c b/repack-promisor.c
index 90318ce150..8fc541d2cf 100644
--- a/repack-promisor.c
+++ b/repack-promisor.c
@@ -4,6 +4,7 @@
 #include "pack.h"
 #include "packfile.h"
 #include "path.h"
+#include "refs.h"
 #include "repository.h"
 #include "run-command.h"
 
@@ -34,6 +35,154 @@ static int write_oid(const struct object_id *oid,
 	return 0;
 }
 
+/*
+ * Go through all .promisor files contained in repo (excluding those whose name
+ * appears in not_repacked_basenames, which acts as a ignorelist), and copies
+ * their content inside the destination file "<packtmp>-<dest_hex>.promisor".
+ * Each line of a never repacked .promisor file is: "<oid> <ref>" (as described
+ * in the write_promisor_file() function).
+ * After a repack, the copied lines will be: "<oid> <ref> <time>", where <time>
+ * is the time (in Unix time) at which the .promisor file was last modified.
+ * Only the lines whose <oid> is present inside "<packtmp>-<dest_hex>.idx" will
+ * be copied.
+ * The contents of all .promisor files are assumed to be correctly formed.
+ */
+static void write_promisor_file_after_repack(struct repository *repo,
+								const char *dest_hex,
+								const char *packtmp,
+								struct strset *not_repacked_basenames)
+{
+	char *dest_promisor_name;
+	char *dest_idx_name;
+	FILE *dest;
+	struct object_id dest_oid;
+	struct packed_git *dest_pack, *p;
+	struct strbuf source_promisor_name = STRBUF_INIT;
+	struct strset seen_lines = STRSET_INIT;
+	struct strbuf line = STRBUF_INIT;
+	int err;
+
+	/* First of all, let's create and open the .promisor dest file */
+	dest_promisor_name = mkpathdup("%s-%s.promisor", packtmp, dest_hex);
+	dest = xfopen(dest_promisor_name, "w");
+
+	/*
+	 * Now let's retrieve the destination pack.
+	 * We use parse_pack_index() because dest_hex/packtmp point to the packfile
+	 * that "pack-objects" just created, which is about to become part of this
+	 * repository, but has not yet been finalized.
+	 * If we are here, we know that "pack-objects" did not fail, so
+	 * parse_pack_index() being loose in validation does not pose a problem.
+	 * If an error happens, we simply leave the ".promisor" file empty.
+	 */
+	if (get_oid_hex_algop(dest_hex, &dest_oid, repo->hash_algo)) {
+		warning(_("Promisor file left empty: '%s' not a hash"), dest_hex);
+		if (fclose(dest))
+			die(_("Could not close '%s' promisor file"), dest_promisor_name);
+		free(dest_promisor_name);
+		return;
+	}
+	dest_idx_name = mkpathdup("%s-%s.idx", packtmp, dest_hex);
+	dest_pack = parse_pack_index(repo, dest_oid.hash, dest_idx_name);
+	if (!dest_pack) {
+		warning(_("Promisor file left empty: couldn't open packfile '%s'"), dest_idx_name);
+		if (fclose(dest))
+			die(_("Could not close '%s' promisor file"), dest_promisor_name);
+		free(dest_promisor_name);
+		free(dest_idx_name);
+		return;
+	}
+
+	repo_for_each_pack(repo, p) {
+		FILE *source;
+		struct stat source_stat;
+
+		if (!p->pack_promisor)
+			continue;
+
+		if (not_repacked_basenames &&
+			strset_contains(not_repacked_basenames, pack_basename(p)))
+			continue;
+
+		strbuf_reset(&source_promisor_name);
+		strbuf_addstr(&source_promisor_name, p->pack_name);
+		strbuf_strip_suffix(&source_promisor_name, ".pack");
+		strbuf_addstr(&source_promisor_name, ".promisor");
+
+		if (stat(source_promisor_name.buf, &source_stat))
+			die(_("File not found: %s"), source_promisor_name.buf);
+
+		source = xfopen(source_promisor_name.buf, "r");
+
+		while (strbuf_getline(&line, source) != EOF) {
+			struct string_list line_sections = STRING_LIST_INIT_DUP;
+			struct object_id oid;
+
+			/* Split line into <oid>, <ref> and <time> (if <time> exists).
+			 * Check that it was actually split into 2 or 3 parts. If it was
+			 *  not, then it is malformed, so skip it.
+			 */
+			string_list_split(&line_sections, line.buf, " ", 3);
+			if (line_sections.nr != 2 && line_sections.nr != 3) {
+				string_list_clear(&line_sections, 0);
+				continue;
+			}
+
+			/* Skip the lines where <oid> is not a sane hexadecimal string */
+			if (get_oid_hex_algop(line_sections.items[0].string,
+						&oid, repo->hash_algo)) {
+				string_list_clear(&line_sections, 0);
+				continue;
+			}
+			/* Ignore the lines where <oid> doesn't appear in the dest_pack */
+			if (!find_pack_entry_one(&oid, dest_pack)) {
+				string_list_clear(&line_sections, 0);
+				continue;
+			}
+
+			/*
+			 * Skip the lines where <ref> does not have the
+			 * correct format for a refname.
+			 */
+			printf("%s\n", line_sections.items[1].string);
+			if (check_refname_format(line_sections.items[1].string,
+							REFNAME_ALLOW_ONELEVEL)) {
+				string_list_clear(&line_sections, 0);
+				continue;
+			}
+
+			/* If <time> doesn't exist, retrieve it and add it to line */
+			if (line_sections.nr != 3)
+				strbuf_addf(&line, " %" PRItime,
+							(timestamp_t)source_stat.st_mtime);
+
+			/* If the finalized line is new, append it to dest */
+			if (strset_add(&seen_lines, line.buf))
+				fprintf(dest, "%s\n", line.buf);
+
+			string_list_clear(&line_sections, 0);
+		}
+
+		err = ferror(source);
+		err |= fclose(source);
+		if (err)
+			die(_("Could not read '%s' promisor file"), source_promisor_name.buf);
+	}
+
+	err = ferror(dest);
+	err |= fclose(dest);
+	if (err)
+		die(_("Could not write '%s' promisor file"), dest_promisor_name);
+
+	close_pack_index(dest_pack);
+	free(dest_pack);
+	free(dest_promisor_name);
+	free(dest_idx_name);
+	strbuf_release(&source_promisor_name);
+	strbuf_release(&line);
+	strset_clear(&seen_lines);
+}
+
 static void finish_repacking_promisor_objects(struct repository *repo,
 					      struct child_process *cmd,
 					      struct string_list *names,

-- 
2.53.0.584.g6b87e8e9dd