Re: [PATCH 3/3] builtin/repack.c: don't move existing packs out of the way

> That is, it is not the case that we pretend as if pack-objects didn't
> write files identical to ones that already exist, but rather that we
> respect what pack-objects wrote as the source of truth. That cuts two
> ways:
>
>   - If pack-objects produced an identical pack to one that already
>     exists with a bitmap, but did not produce a bitmap, we remove the
>     bitmap that already exists. (This behavior is codified in t7700.14).
>
>   - If pack-objects produced an identical pack to one that already
>     exists, we trust the just-written version of the coresponding .idx,
>     .promisor, and other files over the ones that already exist. This
>     ensures that we use the most up-to-date versions of this files,
>     which is safe even in the face of format changes in, say, the .idx
>     file (which would not be reflected in the .idx file's name).

>
> Helped-by: Jeff King <peff@peff.net>
> Signed-off-by: Taylor Blau <me@ttaylorr.com>
> ---
>  builtin/repack.c | 103 +++++++----------------------------------------
>  1 file changed, 14 insertions(+), 89 deletions(-)
>
> diff --git a/builtin/repack.c b/builtin/repack.c
> index bb839180da..279be11a16 100644
> --- a/builtin/repack.c
> +++ b/builtin/repack.c
> @@ -306,7 +306,7 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
>  	struct string_list rollback = STRING_LIST_INIT_NODUP;
>  	struct string_list existing_packs = STRING_LIST_INIT_DUP;
>  	struct strbuf line = STRBUF_INIT;
> -	int i, ext, ret, failed;
> +	int i, ext, ret;
>  	FILE *out;
>
>  	/* variables to be filled by option parsing */
> @@ -463,109 +463,34 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
>
>  	/*
>  	 * Ok we have prepared all new packfiles.
> -	 * First see if there are packs of the same name and if so
> -	 * if we can move them out of the way (this can happen if we
> -	 * repacked immediately after packing fully.
>  	 */
> -	failed = 0;
>  	for_each_string_list_item(item, &names) {
>  		for (ext = 0; ext < ARRAY_SIZE(exts); ext++) {
>  			char *fname, *fname_old;
>
> -			fname = mkpathdup("%s/pack-%s%s", packdir,
> -						item->string, exts[ext].name);
> -			if (!file_exists(fname)) {
> -				free(fname);
> -				continue;
> -			}
> -
> -			fname_old = mkpathdup("%s/old-%s%s", packdir,
> -						item->string, exts[ext].name);
> -			if (file_exists(fname_old))
> -				if (unlink(fname_old))
> -					failed = 1;
> -
> -			if (!failed && rename(fname, fname_old)) {
> -				free(fname);
> -				free(fname_old);
> -				failed = 1;
> -				break;
> -			} else {
> -				string_list_append(&rollback, fname);
> -				free(fname_old);
> -			}
> -		}
> -		if (failed)
> -			break;
> -	}
> -	if (failed) {
> -		struct string_list rollback_failure = STRING_LIST_INIT_DUP;
> -		for_each_string_list_item(item, &rollback) {
> -			char *fname, *fname_old;
> -			fname = mkpathdup("%s/%s", packdir, item->string);
> -			fname_old = mkpathdup("%s/old-%s", packdir, item->string);
> -			if (rename(fname_old, fname))
> -				string_list_append(&rollback_failure, fname);
> -			free(fname);
> -			free(fname_old);
> -		}
> -
> -		if (rollback_failure.nr) {
> -			int i;
> -			fprintf(stderr,
> -				_("WARNING: Some packs in use have been renamed by\n"
> -				  "WARNING: prefixing old- to their name, in order to\n"
> -				  "WARNING: replace them with the new version of the\n"
> -				  "WARNING: file.  But the operation failed, and the\n"
> -				  "WARNING: attempt to rename them back to their\n"
> -				  "WARNING: original names also failed.\n"
> -				  "WARNING: Please rename them in %s manually:\n"), packdir);
> -			for (i = 0; i < rollback_failure.nr; i++)
> -				fprintf(stderr, "WARNING:   old-%s -> %s\n",
> -					rollback_failure.items[i].string,
> -					rollback_failure.items[i].string);
> -		}
> -		exit(1);
> -	}
> -
> -	/* Now the ones with the same name are out of the way... */
> -	for_each_string_list_item(item, &names) {
> -		for (ext = 0; ext < ARRAY_SIZE(exts); ext++) {
> -			char *fname, *fname_old;
> -			struct stat statbuffer;
> -			int exists = 0;
>  			fname = mkpathdup("%s/pack-%s%s",
>  					packdir, item->string, exts[ext].name);
>  			fname_old = mkpathdup("%s-%s%s",
>  					packtmp, item->string, exts[ext].name);
> -			if (!stat(fname_old, &statbuffer)) {
> -				statbuffer.st_mode &= ~(S_IWUSR | S_IWGRP | S_IWOTH);
> -				chmod(fname_old, statbuffer.st_mode);
> -				exists = 1;
> -			}
> -			if (exists || !exts[ext].optional) {
> +
> +			if (((uintptr_t)item->util) & (1 << ext)) {
> +				struct stat statbuffer;
> +				if (!stat(fname_old, &statbuffer)) {
> +					statbuffer.st_mode &= ~(S_IWUSR | S_IWGRP | S_IWOTH);
> +					chmod(fname_old, statbuffer.st_mode);
> +				}
> +
>  				if (rename(fname_old, fname))
>  					die_errno(_("renaming '%s' failed"), fname_old);
> -			}
> +			} else if (!exts[ext].optional)
> +				die(_("missing required file: %s"), fname_old);
> +			else if (unlink(fname) < 0 && errno != ENOENT)
> +				die_errno(_("could not unlink: %s"), fname);
> +
>  			free(fname);
>  			free(fname_old);
>  		}
>  	}
> -
> -	/* Remove the "old-" files */
> -	for_each_string_list_item(item, &names) {
> -		for (ext = 0; ext < ARRAY_SIZE(exts); ext++) {
> -			char *fname;
> -			fname = mkpathdup("%s/old-%s%s",
> -					  packdir,
> -					  item->string,
> -					  exts[ext].name);
> -			if (remove_path(fname))
> -				warning(_("failed to remove '%s'"), fname);
> -			free(fname);
> -		}
> -	}
> -
>  	/* End of pack replacement. */
>
>  	reprepare_packed_git(the_repository);
> --
> 2.29.2.312.gabc4d358d8