On Fri, Jan 27, 2017 at 01:38:55PM +0100, Johannes Schindelin wrote:

> Just like with other Git commands, this option makes it read the paths
> from the standard input. It comes in handy when resetting many, many
> paths at once and wildcards are not an option (e.g. when the paths are
> generated by a tool).
> 
> Note: we first parse the entire list and perform the actual reset action
> only in a second phase. Not only does this make things simpler, it also
> helps performance, as do_diff_cache() traverses the index and the
> (sorted) pathspecs in simultaneously to avoid unnecessary lookups.

This looks OK to me. At first I wondered if using PATHSPEC_LITERAL_PATH
was consistent with other "--stdin" tools. I think it mostly is (or at
least consistent with checkout-index). The exception is "rev-list
--stdin", but that's probably fine. It is taking rev-list arguments in
the first place, not a list of paths.

A few minor suggestions:

> +--stdin::
> +     Instead of taking list of paths from the command line,
> +     read list of paths from the standard input.  Paths are
> +     separated by LF (i.e. one path per line) by default.
> +
> +-z::
> +     Only meaningful with `--stdin`; paths are separated with
> +     NUL character instead of LF.

Is it worth clarifying that these are paths, not pathspecs? The word
"paths" is used to refer to the pathspecs on the command-line elsewhere
in the document.

It might also be worth mentioning the quoting rules for the non-z case.

> @@ -267,7 +270,9 @@ static int reset_refs(const char *rev, const struct 
> object_id *oid)
>  int cmd_reset(int argc, const char **argv, const char *prefix)
>  {
>       int reset_type = NONE, update_ref_status = 0, quiet = 0;
> -     int patch_mode = 0, unborn;
> +     int patch_mode = 0, nul_term_line = 0, read_from_stdin = 0, unborn;
> +     char **stdin_paths = NULL;
> +     int stdin_nr = 0, stdin_alloc = 0;

This list is a good candidate for an argv_array, I think. So:

  struct argv_array stdin_paths = ARGV_ARRAY_INIT;

> +                     ALLOC_GROW(stdin_paths, stdin_nr + 1, stdin_alloc);
> +                     stdin_paths[stdin_nr++] = xstrdup(buf.buf);

  argv_array_push(&stdin_paths, buf.buf);

> +             ALLOC_GROW(stdin_paths, stdin_nr + 1, stdin_alloc);
> +             stdin_paths[stdin_nr++] = NULL;

  This goes away because argv_array handles it for you.

> +     if (stdin_paths) {
> +             while (stdin_nr)
> +                     free(stdin_paths[--stdin_nr]);
> +             free(stdin_paths);
> +     }

  argv_array_clear(&stdin_paths);

> @@ -295,6 +304,43 @@ int cmd_reset(int argc, const char **argv, const char 
> *prefix)
>                                               PARSE_OPT_KEEP_DASHDASH);
>       parse_args(&pathspec, argv, prefix, patch_mode, &rev);
>  
> +     if (read_from_stdin) {
> +             strbuf_getline_fn getline_fn = nul_term_line ?
> +                     strbuf_getline_nul : strbuf_getline_lf;
> +             int flags = PATHSPEC_PREFER_FULL |
> +                     PATHSPEC_STRIP_SUBMODULE_SLASH_CHEAP;

You set two flags here...

> +             ALLOC_GROW(stdin_paths, stdin_nr + 1, stdin_alloc);
> +             stdin_paths[stdin_nr++] = NULL;
> +             flags |= PATHSPEC_LITERAL_PATH;
> +             parse_pathspec(&pathspec, 0, flags, prefix,
> +                            (const char **)stdin_paths);

...and then one more here. They all seem to be set unconditionally, and
we never look at "flags" between the two lines. I think it would be more
obvious to set them all in the same place.

> +     } else if (nul_term_line)
> +             die(_("-z requires --stdin"));
> +

Hmm, there's our brace question coming up again. :)

> diff --git a/t/t7107-reset-stdin.sh b/t/t7107-reset-stdin.sh
> new file mode 100755
> index 0000000000..997dc42dd2
> --- /dev/null
> +++ b/t/t7107-reset-stdin.sh
> @@ -0,0 +1,33 @@
> +#!/bin/sh
> +
> +test_description='reset --stdin'

Here are a few things we might want to test that I didn't see covered:

  - feeding path X does not reset path Y

  - de-quoting in the non-z case

-Peff

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