Re: [PATCH 1/3] submodule: implement `module_list` as a builtin helper

> Most of the submodule operations work on a set of submodules.
> Calculating and using this set is usually done via:
>
>        module_list "$@" | {
>            while read mode sha1 stage sm_path
>            do
>                 # the actual operation
>            done
>        }
>
> Currently the function `module_list` is implemented in the
> git-submodule.sh as a shell script wrapping a perl script.
> The rewrite is in C, such that it is faster and can later be
> easily adapted when other functions are rewritten in C.
>
> git-submodule.sh similar to the builtin commands will navigate
> to the top most directory of the repository and keeping the
> subdirectories as a variable.

> Signed-off-by: Stefan Beller <sbeller@google.com>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
> diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
> new file mode 100644
> index 0000000..beaab7d
> --- /dev/null
> +++ b/builtin/submodule--helper.c
> @@ -0,0 +1,114 @@
> +#include "builtin.h"
> +#include "cache.h"
> +#include "parse-options.h"
> +#include "quote.h"
> +#include "pathspec.h"
> +#include "dir.h"
> +#include "utf8.h"
> +
> +static const struct cache_entry **ce_entries;
> +static int ce_alloc, ce_used;
> +static const char *alternative_path;

> +static int module_list_compute(int argc, const char **argv,
> +                               const char *prefix,
> +                               struct pathspec *pathspec)
> +{
> +       int i;
> +       char *max_prefix, *ps_matched = NULL;
> +       int max_prefix_len;
> +       parse_pathspec(pathspec, 0,
> +                      PATHSPEC_PREFER_FULL |
> +                      PATHSPEC_STRIP_SUBMODULE_SLASH_CHEAP,
> +                      prefix, argv);
> +
> +       /* Find common prefix for all pathspec's */
> +       max_prefix = common_prefix(pathspec);
> +       max_prefix_len = max_prefix ? strlen(max_prefix) : 0;
> +
> +       if (pathspec->nr)
> +               ps_matched = xcalloc(pathspec->nr, 1);
> +
> +       if (read_cache() < 0)
> +               die("index file corrupt");
> +
> +       for (i = 0; i < active_nr; i++) {
> +               const struct cache_entry *ce = active_cache[i];
> +
> +               if (!match_pathspec(pathspec, ce->name, ce_namelen(ce),
> +                                   max_prefix_len, ps_matched,
> +                                   S_ISGITLINK(ce->ce_mode) | S_ISDIR(ce->ce_mode)))
> +                       continue;
> +
> +               if (S_ISGITLINK(ce->ce_mode)) {
> +                       ALLOC_GROW(ce_entries, ce_used + 1, ce_alloc);
> +                       ce_entries[ce_used++] = ce;
> +               }
> +
> +               while (i + 1 < active_nr && !strcmp(ce->name, active_cache[i + 1]->name))
> +                       /*
> +                        * Skip entries with the same name in different stages
> +                        * to make sure an entry is returned only once.
> +                        */
> +                       i++;
> +       }
> +       free(max_prefix);
> +
> +       if (ps_matched && report_path_error(ps_matched, pathspec, prefix))
> +               return -1;
> +
> +       return 0;

> +}
> +
> +static int module_list(int argc, const char **argv, const char *prefix)
> +{
> +       int i;
> +       static struct pathspec pathspec;

> +
> +       struct option module_list_options[] = {
> +               OPT_STRING(0, "prefix", &alternative_path,
> +                          N_("path"),
> +                          N_("alternative anchor for relative paths")),
> +               OPT_END()
> +       };
> +
> +       static const char * const git_submodule_helper_usage[] = {

> +               N_("git submodule--helper module_list [--prefix=<path>] [<path>...]"),
> +               NULL
> +       };
> +
> +       argc = parse_options(argc, argv, prefix, module_list_options,
> +                            git_submodule_helper_usage, 0);
> +
> +       if (module_list_compute(argc, argv, alternative_path
> +                                           ? alternative_path
> +                                           : prefix, &pathspec) < 0) {
> +               printf("#unmatched\n");
> +               return 1;
> +       }
> +
> +       for (i = 0; i < ce_used; i++) {
> +               const struct cache_entry *ce = ce_entries[i];
> +
> +               if (ce_stage(ce)) {
> +                       printf("%06o %s U\t", ce->ce_mode, sha1_to_hex(null_sha1));
> +               } else {
> +                       printf("%06o %s %d\t", ce->ce_mode, sha1_to_hex(ce->sha1), ce_stage(ce));
> +               }

> +               utf8_fprintf(stdout, "%s\n", ce->name);
> +       }
> +       return 0;
> +}
> +
> +int cmd_submodule__helper(int argc, const char **argv, const char *prefix)
> +{
> +       if (argc < 2)
> +               goto usage;
> +
> +       if (!strcmp(argv[1], "module_list"))
> +               return module_list(argc - 1, argv + 1, prefix);
> +
> +usage:
> +       usage("git submodule--helper module_list\n");