Re: [RFC PATCHv4] repack: rewrite the shell script in C.

On 08/20/2013 03:31 PM, Johannes Sixt wrote:

Are the long forms of options your invention?

I tried to keep strong similarity with the shell script for
ease of review. In the shellscript the options where 
put in variables having these names, so for example there was:

	-f)	no_reuse=--no-reuse-delta ;;
	-F)	no_reuse=--no-reuse-object ;;

So I used these variable names as well in here. And as I assumed
the variables are meaningful in itself.

In the shell script they may be meaningful, but with the option
parser in the C version, I overlooked the possibility for 
--no-<option> being possible as you noted below.

Maybe we should inverse the logic and have the variables and options
called reuse-delta and being enabled by default.

quoted

+        OPT_BOOL('a', "all", &pack_everything,
+                N_("pack everything in a single pack")),
+        OPT_BOOL('A', "all-but-loose", &pack_everything_but_loose,
+                N_("same as -a, and turn unreachable objects loose")),

--all-but-loose does not express what the help text says. The long form
of -A is --all --unpack-unreachable, so it is really just a short option
for convenience. It does not need its own long form.

Ok, I'll keep that in mind, and will only use the varialbe tied to -A
to set the -a and --unpack-unreachable variable.

quoted

+        OPT_BOOL('d', "delete-redundant", &delete_redundant,
+                N_("remove redundant packs, and run git-prune-packed")),
+        OPT_BOOL('f', "no-reuse-delta", &no_reuse_delta,
+                N_("pass --no-reuse-delta to git-pack-objects")),
+        OPT_BOOL('F', "no-reuse-object", &no_reuse_object,
+                N_("pass --no-reuse-object to git-pack-objects")),

Do we want to allow --no-no-reuse-delta and --no-no-reuse-object?

see above, I'd try not to.

quoted

+        OPT_BOOL('n', NULL, &no_update_server_info,
+                N_("do not run git-update-server-info")),

No long option name?

This is also a negated option, so as above, maybe 
we could have --update_server_info and --no-update_server_info
respectively. Talking about the shortform then: Is it possible to
negate the shortform?

quoted

+        OPT__QUIET(&quiet, N_("be quiet")),
+        OPT_BOOL('l', "local", &local,
+                N_("pass --local to git-pack-objects")),

Good.

quoted

+        OPT_STRING(0, "unpack-unreachable", &unpack_unreachable,
N_("approxidate"),
+                N_("with -A, do not loosen objects older than this
Packing constraints")),

"Packing constraints" is a section heading, not a continuation of the
previous help text.

quoted

+        OPT_INTEGER(0, "window", &window,
+                N_("size of the window used for delta compression")),

This help text is suboptimal as the option is a count, not a "size" in
the narrow sense. But that can be changed later (as it would affect
other tools as well, I guess).

quoted

+        OPT_INTEGER(0, "window-memory", &window_memory,
+                N_("same as the above, but limit memory size instead
of entries count")),
+        OPT_INTEGER(0, "depth", &depth,
+                N_("limits the maximum delta depth")),
+        OPT_INTEGER(0, "max-pack-size", &max_pack_size,
+                N_("maximum size of each packfile")),
+        OPT_END()
+    };

Good.

quoted

+
+    git_config(repack_config, NULL);
+
+    argc = parse_options(argc, argv, prefix, builtin_repack_options,
+                git_repack_usage, 0);
+
+    sigchain_push_common(remove_pack_on_signal);

Good.

quoted

+    packdir = mkpathdup("%s/pack", get_object_directory());
+    packtmp = mkpathdup("%s/.tmp-%d-pack", packdir, getpid());

Should this not be

    packdir = xstrdup(git_path("pack"));
    packtmp = xstrdup(git_path("pack/.tmp-%d-pack", getpid()));

Perhaps make packdir and packtmp global so that the strings need not be
duplicated in get_pack_filenames and remove_temporary_files?

ok

quoted

+
+    remove_temporary_files();

Yes, the shell script had this. But is it really necessary?

Well I can drop it if it's not needed.
It actually should implement
	rm -f "$PACKTMP"-*
and then the trap 'rm -f "$PACKTMP"-*' 0 1 2 3 15
as well.

quoted

+
+    struct argv_array cmd_args = ARGV_ARRAY_INIT;

Declaration after statement.

will fix.

quoted

+    argv_array_push(&cmd_args, "pack-objects");
+    argv_array_push(&cmd_args, "--keep-true-parents");
+    argv_array_push(&cmd_args, "--honor-pack-keep");
+    argv_array_push(&cmd_args, "--non-empty");
+    argv_array_push(&cmd_args, "--all");
+    argv_array_push(&cmd_args, "--reflog");
+
+    if (window)
+        argv_array_pushf(&cmd_args, "--window=%u", window);
+
+    if (window_memory)
+        argv_array_pushf(&cmd_args, "--window-memory=%u",
window_memory);
+
+    if (depth)
+        argv_array_pushf(&cmd_args, "--depth=%u", depth);
+
+    if (max_pack_size)
+        argv_array_pushf(&cmd_args, "--max_pack_size=%u",
max_pack_size);
+
+    if (no_reuse_delta)
+        argv_array_pushf(&cmd_args, "--no-reuse-delta");
+
+    if (no_reuse_object)
+        argv_array_pushf(&cmd_args, "--no-reuse-object");

no_reuse_delta and no_reuse_object are mutually exclusive, according to
the shell script version.

I'll change it then to OPT_BIT and die() when both are set.

quoted

+
+    if (pack_everything + pack_everything_but_loose == 0) {
+        argv_array_push(&cmd_args, "--unpacked");
+        argv_array_push(&cmd_args, "--incremental");
+    } else {
+        struct string_list fname_list = STRING_LIST_INIT_DUP;
+        get_pack_filenames(packdir, &fname_list);
+        for_each_string_list_item(item, &fname_list) {
+            char *fname;
+            fname = mkpathdup("%s/%s.keep", packdir, item->string);
+            if (stat(fname, &statbuffer) &&
S_ISREG(statbuffer.st_mode)) {

            if (!stat(fname, &statbuffer) && ...

But you are using file_exists() later. That should be good enough here
as well, no?

will do.

quoted

+                /* when the keep file is there, we're ignoring that
pack */
+            } else {
+                string_list_append(&existing_packs, item->string);
+            }
+            free(fname);
+        }
+
+        if (existing_packs.nr && delete_redundant) {
+            if (unpack_unreachable)
+                argv_array_pushf(&cmd_args,
"--unpack-unreachable=%s", unpack_unreachable);
+            else if (pack_everything_but_loose)
+                argv_array_push(&cmd_args, "--unpack-unreachable");
+        }
+    }
+
+    if (local)
+        argv_array_push(&cmd_args,  "--local");
+    if (quiet)
+        argv_array_push(&cmd_args,  "--quiet");
+    if (delta_base_offset)
+        argv_array_push(&cmd_args,  "--delta-base-offset");
+
+    argv_array_push(&cmd_args, packtmp);

Otherwise, argument setup looks fine.

quoted

+
+    memset(&cmd, 0, sizeof(cmd));
+    cmd.argv = argv_array_detach(&cmd_args, NULL);

Is it necessary to detach the arguments?

Probably not. 

quoted

+    cmd.git_cmd = 1;
+    cmd.out = -1;
+    cmd.no_stdin = 1;
+
+    if (run_command(&cmd))
+        return 1;

You cannot run_command() and then later read its output! You must split
it into start_command(), read stdout, finish_command().

Thanks for this hint. Could that explain rare non-deterministic failures in
the test suite?

quoted

+
+    struct string_list names = STRING_LIST_INIT_DUP;
+    struct string_list rollback = STRING_LIST_INIT_DUP;

Declaration after statement.

will fix

quoted

+
+    char line[1024];
+    int counter = 0;
+    FILE *out = xfdopen(cmd.out, "r");
+    while (fgets(line, sizeof(line), out)) {
+        /* a line consists of 40 hex chars + '\n' */
+        assert(strlen(line) == 41);

You cannot make assertions about input that you read from an external
command! You can die() if the expectation is not met. But I think that
in this case the only necessary expectation is that a line is not empty.

BTW, don't we have strbuf functions to read from an fd linewise?

I'll check.

quoted

+        line[40] = '\0';
+        string_list_append(&names, line);
+        counter++;
+    }
+    if (!counter)
+        printf("Nothing new to pack.\n");

This was 'say Nothing new to pack.'. say obeys --quiet, IIRC.

ok

quoted

+    fclose(out);
+
+    int failed = 0;
+    for_each_string_list_item(item, &names) {
+        for (ext = 0; ext < 1; ext++) {
+            char *fname, *fname_old;
+            fname = mkpathdup("%s/%s%s", packdir, item->string,
exts[ext]);
+            if (!file_exists(fname)) {
+                free(fname);
+                continue;
+            }
+
+            fname_old = mkpathdup("%s/old-%s%s", packdir,
item->string, exts[ext]);

If you could use git_path() instead of mkpathdup() in these two cases,
we would not need to free() the names.

quoted

+            if (file_exists(fname_old))
+                unlink(fname_old);
+
+            if (rename(fname, fname_old)) {
+                failed = 1;
+                break;
+            }
+            free(fname_old);
+            string_list_append_nodup(&rollback, fname);

Ah, we would need to allocate here then.

quoted

+        }
+        if (failed)
+            /* set to last element to break for_each loop */
+            item = names.items + names.nr;

A mere
            break;
doesn't do it here?

Sure! I'll replace by break.

quoted

+    }
+    if (failed) {
+        struct string_list rollback_failure;
+        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);

I think it's possible to attach arbitrary data to each string_list item.
We could attach the "%s/old-%s" name to the item name, then we wouldn't
need to re-construct the names here.

handy! I'll try to do that.

quoted

+            if (rename(fname_old, fname))
+                string_list_append(&rollback_failure, fname);
+            free(fname);
+            free(fname_old);
+        }
+
+        if (rollback.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 $PACKDIR manually:\n");
+            for (i = 0; i < rollback.nr; i++)
+                fprintf(stderr, "WARNING:   old-%s -> %s\n",
+                    rollback.items[i].string,
+                    rollback.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 < 2; ext++) {
+            char *fname, *fname_old;
+            fname = mkpathdup("%s/pack-%s%s", packdir, item->string,
exts[ext]);
+            fname_old = mkpathdup("%s-%s%s", packtmp, item->string,
exts[ext]);

Same here: git_path()?

quoted

+            stat(fname_old, &statbuffer);

We ignore errors during chmod in the shell script. But this doesn't give
you license to ignore stat() errors completely: If stat() fails, then
don't chmod() below, either.

ok

quoted

+            statbuffer.st_mode &= ~S_IWUSR | ~S_IWGRP | ~S_IWOTH;

            statbuffer.st_mode &= ~(S_IWUSR|S_IWGRP|S_IWOTH);

quoted

+            chmod(fname_old, statbuffer.st_mode);
+            if (rename(fname_old, fname))
+                die("Could not rename packfile: %s -> %s", fname_old,
fname);

Use die_errno() here.

quoted

+            free(fname);
+            free(fname_old);
+        }
+    }
+
+    /* Remove the "old-" files */
+    for_each_string_list_item(item, &names) {
+        char *fname;
+        fname = mkpathdup("%s/old-pack-%s.idx", packdir, item->string);
+        if (remove_path(fname))
+            die("Could not remove file: %s", fname);

die_errno() makes sense here, too.

quoted

+        free(fname);
+
+        fname = mkpathdup("%s/old-pack-%s.pack", packdir, item->string);
+        if (remove_path(fname))
+            die("Could not remove file: %s", fname);

and here as well.

quoted

+        free(fname);

Again git_path?

quoted

+    }
+
+    /* End of pack replacement. */

Nit: A blank line should follow this comment.

quoted

+    if (delete_redundant) {
+        sort_string_list(&names);
+        for_each_string_list_item(item, &existing_packs) {
+            char *sha1;
+            size_t len = strlen(item->string);
+            if (len < 40)
+                continue;
+            sha1 = item->string + len - 40;
+            if (!string_list_has_string(&names, sha1))
+                remove_pack(packdir, item->string);
+        }

OK.

quoted

+        argv_array_clear(&cmd_args);
+        argv_array_push(&cmd_args, "prune-packed");
+        if (quiet)
+            argv_array_push(&cmd_args, "--quiet");
+
+        memset(&cmd, 0, sizeof(cmd));
+        cmd.argv = argv_array_detach(&cmd_args, NULL);

Again: is it necessary to detach?

quoted

+        cmd.git_cmd = 1;
+        run_command(&cmd);
+    }
+
+    if (!no_update_server_info) {
+        argv_array_clear(&cmd_args);
+        argv_array_push(&cmd_args, "update-server-info");
+
+        memset(&cmd, 0, sizeof(cmd));
+        cmd.argv = argv_array_detach(&cmd_args, NULL);

Same here?

quoted

+        cmd.git_cmd = 1;
+        run_command(&cmd);
+    }
+    return 0;
+}

In my opinion, it is good that you keep a large function that resembles
the structure of the shell script because it is easier to review. But
ultimately, it should be factored into smaller functions.

-- Hannes

Hannes,

thank you very much for the review. I'll follow your suggestions and dive
deeper into the API to change your annotated lines.

Thanks,
Stefan