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From: Linus Arver <linusa@google.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: Linus Arver via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org, Glen Choo <glencbz@gmail.com>,
	Christian Couder <chriscool@tuxfamily.org>,
	Phillip Wood <phillip.wood123@gmail.com>
Subject: Re: [PATCH v2 4/6] trailer: teach find_patch_start about --no-divider
Date: Wed, 13 Sep 2023 22:31:40 -0700	[thread overview]
Message-ID: <owlyttrxjp6r.fsf@fine.c.googlers.com> (raw)
In-Reply-To: <xmqq5y4dla6p.fsf@gitster.g>

Junio C Hamano <gitster@pobox.com> writes:

> Linus Arver <linusa@google.com> writes:
>
>>> The real purpose of this function is to find the end of the log
>>> message, isn't it?
>>
>> Indeed.
>> ...
>> Right! So a better name might be something like
>> "find_trailer_search_boundary" with a comment like
>
> Or "find_end_of_log_message()", which we agreed to be the real
> purpose of this function ;-)

I did this locally, but in doing so realized that we have in trailer.c

    /* Return the position of the end of the trailers. */
    static size_t find_trailer_end(const char *buf, size_t len)
    {
        return len - ignore_non_trailer(buf, len);
    }

and the ignore_non_trailer() comes from commit.c, which says

    /*
    * Inspect the given string and determine the true "end" of the log message, in
    * order to find where to put a new Signed-off-by trailer.  Ignored are
    * trailing comment lines and blank lines.  To support "git commit -s
    * --amend" on an existing commit, we also ignore "Conflicts:".  To
    * support "git commit -v", we truncate at cut lines.
    *
    * Returns the number of bytes from the tail to ignore, to be fed as
    * the second parameter to append_signoff().
    */
    size_t ignore_non_trailer(const char *buf, size_t len)
    {

...and I am not so sure the new "find_end_of_log_message" name for
find_patch_start() is desirable because of the overlap in meaning with
the comment for ignore_non_trailer(). To recap, we have in
trailer_info_get() in trailer.c which (without this patch) has

    if (opts->no_divider)
        patch_start = strlen(str);
    else
        patch_start = find_patch_start(str);

    trailer_end = find_trailer_end(str, patch_start);
    trailer_start = find_trailer_start(str, trailer_end);
                
to find the trailer_end and trailer_start positions in the input. These
positions are the boundaries for parsing for actual trailers (if any).
More precisely, the "patch_start" variable helps us _skip_ the "patch
part" of the input (if any, denoted by "---"). The call to
find_trailer_end() helps us (again) _skip_ any parts that are not part
of the actual log message (per the comment in ignore_non_trailer()). So
as far as trailer_info_get() is concerned, we are just trying to skip
over areas where we shouldn't search/parse for trailers.

The above analysis leads me to some new ideas:

(1) For "find_end_of_log_message()", I think this name should really
    belong to ignore_non_trailer() in commit.c instead of
    find_patch_start() in trailer.c. The existing comment for
    ignore_non_trailer() already says that its job is to determine the
    true end of the log message (and does a lot of the necessary work to
    do this job).

(2) find_patch_start() should be named something like
    "shrink_trailer_search_space" (although this meaning belongs equally
    well to find_trailer_end()), because the point is to reduce the
    search space for parsing trailers.

(3) "find_trailer_end" is not a great function name because on first
    glance it implies that it found the end of trailers, but this is
    only true for the "happy path" of actually finding trailers.

I need to consider all of the above ideas and reroll this patch. Because
the ideas here closely relate to the "trailer_end" and "trailer_start"
variables, I will probably reorder the series so that this patch and the
last patch are closer together.

  reply	other threads:[~2023-09-14  5:31 UTC|newest]

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-05  5:04 [PATCH 0/5] Trailer readability cleanups Linus Arver via GitGitGadget
2023-08-05  5:04 ` [PATCH 1/5] trailer: separate public from internal portion of trailer_iterator Linus Arver via GitGitGadget
2023-08-07 21:16   ` Glen Choo
2023-08-08 12:19     ` Phillip Wood
2023-08-10 23:15       ` Linus Arver
2023-08-10 22:50     ` Linus Arver
2023-08-05  5:04 ` [PATCH 2/5] trailer: split process_input_file into separate pieces Linus Arver via GitGitGadget
2023-08-07 22:39   ` Glen Choo
2023-08-11  0:41     ` Linus Arver
2023-08-05  5:04 ` [PATCH 3/5] trailer: split process_command_line_args into separate functions Linus Arver via GitGitGadget
2023-08-07 22:51   ` Glen Choo
2023-08-11  0:59     ` Linus Arver
2023-08-11  1:02       ` Linus Arver
2023-08-11 21:11       ` Glen Choo
2023-08-05  5:04 ` [PATCH 4/5] trailer: teach find_patch_start about --no-divider Linus Arver via GitGitGadget
2023-08-07 23:28   ` Glen Choo
2023-08-11  1:25     ` Linus Arver
2023-08-11 20:51       ` Glen Choo
2023-08-05  5:04 ` [PATCH 5/5] trailer: rename *_DEFAULT enums to *_UNSPECIFIED Linus Arver via GitGitGadget
2023-08-07 23:45   ` Glen Choo
2023-08-11 18:00     ` Linus Arver
2023-09-09  6:16 ` [PATCH v2 0/6] Trailer readability cleanups Linus Arver via GitGitGadget
2023-09-09  6:16   ` [PATCH v2 1/6] trailer: separate public from internal portion of trailer_iterator Linus Arver via GitGitGadget
2023-09-11 17:10     ` Junio C Hamano
2023-09-09  6:16   ` [PATCH v2 2/6] trailer: split process_input_file into separate pieces Linus Arver via GitGitGadget
2023-09-11 17:10     ` Junio C Hamano
2023-09-09  6:16   ` [PATCH v2 3/6] trailer: split process_command_line_args into separate functions Linus Arver via GitGitGadget
2023-09-09  6:16   ` [PATCH v2 4/6] trailer: teach find_patch_start about --no-divider Linus Arver via GitGitGadget
2023-09-11 17:25     ` Junio C Hamano
2023-09-14  2:19       ` Linus Arver
2023-09-14  3:12         ` Junio C Hamano
2023-09-14  5:31           ` Linus Arver [this message]
2023-09-09  6:16   ` [PATCH v2 5/6] trailer: rename *_DEFAULT enums to *_UNSPECIFIED Linus Arver via GitGitGadget
2023-09-11 18:54     ` Junio C Hamano
2023-09-14  2:41       ` Linus Arver
2023-09-14  3:16         ` Junio C Hamano
2023-09-22 18:23           ` Linus Arver
2023-09-22 19:48             ` Junio C Hamano
2023-09-26  5:30               ` Linus Arver
2023-09-09  6:16   ` [PATCH v2 6/6] trailer: use offsets for trailer_start/trailer_end Linus Arver via GitGitGadget
2023-09-11 19:01     ` Junio C Hamano
2023-09-14  1:21       ` Linus Arver
2023-09-14  3:18         ` Linus Arver
2023-09-22 19:50   ` [PATCH v3 0/9] Trailer readability cleanups Linus Arver via GitGitGadget
2023-09-22 19:50     ` [PATCH v3 1/9] trailer: separate public from internal portion of trailer_iterator Linus Arver via GitGitGadget
2023-09-22 19:50     ` [PATCH v3 2/9] trailer: split process_input_file into separate pieces Linus Arver via GitGitGadget
2023-09-22 19:50     ` [PATCH v3 3/9] trailer: split process_command_line_args into separate functions Linus Arver via GitGitGadget
2023-09-22 19:50     ` [PATCH v3 4/9] trailer: rename *_DEFAULT enums to *_UNSPECIFIED Linus Arver via GitGitGadget
2023-09-22 19:50     ` [PATCH v3 5/9] commit: ignore_non_trailer computes number of bytes to ignore Linus Arver via GitGitGadget
2023-09-22 19:50     ` [PATCH v3 6/9] trailer: find the end of the log message Linus Arver via GitGitGadget
2023-09-22 19:50     ` [PATCH v3 7/9] trailer: use offsets for trailer_start/trailer_end Linus Arver via GitGitGadget
2023-09-22 19:50     ` [PATCH v3 8/9] trailer: only use trailer_block_* variables if trailers were found Linus Arver via GitGitGadget
2023-09-22 19:50     ` [PATCH v3 9/9] trailer: make stack variable names match field names Linus Arver via GitGitGadget
2023-09-22 22:47     ` [PATCH v3 0/9] Trailer readability cleanups Junio C Hamano
2023-09-22 23:13       ` Linus Arver
2023-09-23  0:48         ` Junio C Hamano
2023-09-26  5:40           ` Linus Arver
2023-09-26  6:22     ` [PATCH v4 0/4] " Linus Arver via GitGitGadget
2023-09-26  6:22       ` [PATCH v4 1/4] commit: ignore_non_trailer computes number of bytes to ignore Linus Arver via GitGitGadget
2023-09-26  6:22       ` [PATCH v4 2/4] trailer: find the end of the log message Linus Arver via GitGitGadget
2023-09-28 23:16         ` Jonathan Tan
2023-10-20  0:24           ` Linus Arver
2023-10-20  0:36             ` Junio C Hamano
2023-09-26  6:22       ` [PATCH v4 3/4] trailer: use offsets for trailer_start/trailer_end Linus Arver via GitGitGadget
2023-09-26  6:22       ` [PATCH v4 4/4] trailer: only use trailer_block_* variables if trailers were found Linus Arver via GitGitGadget
2023-10-20 19:01       ` [PATCH v5 0/3] Trailer readability cleanups Linus Arver via GitGitGadget
2023-10-20 19:01         ` [PATCH v5 1/3] commit: ignore_non_trailer computes number of bytes to ignore Linus Arver via GitGitGadget
2023-10-20 19:01         ` [PATCH v5 2/3] trailer: find the end of the log message Linus Arver via GitGitGadget
2023-10-20 21:29           ` Junio C Hamano
2023-12-29  6:42             ` Linus Arver
2023-12-29 21:03               ` Linus Arver
2023-10-20 19:01         ` [PATCH v5 3/3] trailer: use offsets for trailer_start/trailer_end Linus Arver via GitGitGadget

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