Re: Clarify the meaning of "character" in the documentation

[Kristoffer Haugsbakk <code@khaugsbakk.name>]

On Tue, Mar 5, 2024, at 16:32, Junio C Hamano wrote:
> "Kristoffer Haugsbakk" <code@khaugsbakk.name> writes:
>
>>> As an example, with
>>> git config --add core.commentChar •  // Bullet (U+2022)
>>> git does not complain, but it is rejected later.
>>
>> I think this is more about `git config --add` not doing any
>> validation. It just sets things. You can do `git config --add
>> core.commentChar 'ffd'` and get the same effect.
>
> This is not wrong per-se, but it merely explains why "config" takes
> it without complaining (the command just does not know anything
> about what each variable means and what the valid range of values
> are).  core.commentChar is limited to "a byte" so in the context of
> everything else (like commit log message in the editor) being UTF-8,
> it means ASCII would only work there.

Yep, I neglected to mention that part.

> I personally do not see a reason, however, why we need to be limited
> to a single byte, though.  If a patch cleanly implements to allow us
> to use any one-or-more-byte sequence as core.commentChar, I do not
> offhand see a good reason to reject it---it would be fully backward
> compatible and allows you to use a UTF-8 charcter outside ASCII, as
> well as "//" and the like.

Allow one codepoint or a string? Since a Unicode “character” can be
composed of multiple codepoints. And at that point it might be more work
to validate that it is a “character” compared to allowing any kind of
string.

Maybe introduce `core.commentString` and make it a synonym for
`core.commentChar`?

> The core part of "diff" is very much line oriented, and after
> chopping your random sequence of bytes at each LF that appears in
> it, the code is pretty oblivious to the character boundary, except
> for a few cases.  "-w" needs to know what the whitespace characters
> are (it knows only the limited basic set like SP HT and probably
> VT), "-i" needs to know that "A" and "a" are equivalent (I think it
> only knows the ASCII, but I may be misremembering).  Outside the
> core part of "diff", there are frills that need to know about
> character boundaries, like chopping the function header comment
> placed on a hunk header "@@ -1682,7 +1682,7 @@" to a reasonable
> length, --color-words/--word-diff that first separates lines into
> multi-character tokens and align matching sequences in them, etc.

Ah, interesting. Thanks :)

> As you said, we should document core.commentChar as limited to an
> ASCII character, at least as a short term solution.

Aha, I see now that the config documentation doesn’t make that clear.

-- >8 --
Subject: [PATCH] config: document `core.commentChar` as ASCII-only

d3b3419f8f2 (config: tell the user that we expect an ASCII character,
2023-03-27) updated an error message to make clear that this option
specifically wants an ASCII character but neglected to consider the
config documentation.

Reported-by: Manlio Perillo <manlio.perillo@gmail.com>
Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
---

Notes (series):
    I didn’t find any other relevant occurences with
    
        git grep 'commentChar' -- ':(exclude)po'
    
    `Documentation/git-commit.txt` mentions it but it doesn’t seem like a
    clarification is needed in that context.

 Documentation/config/core.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/config/core.txt b/Documentation/config/core.txt
index 0e8c2832bf9..2d4bbdb25fa 100644
--- a/Documentation/config/core.txt
+++ b/Documentation/config/core.txt
@@ -521,7 +521,7 @@ core.editor::
 
 core.commentChar::
 	Commands such as `commit` and `tag` that let you edit
-	messages consider a line that begins with this character
+	messages consider a line that begins with this ASCII character
 	commented, and removes them after the editor returns
 	(default '#').
 +
-- 
2.44.0.64.g52b67adbeb2