Re: [PATCH 2/2] t3430: update to test with custom commentChar

[Daniel Harding <dharding@living180.net>]

Hi Johannes,

On Tue, 10 Jul 2018 at 16:08:57 +0300, Johannes Schindelin wrote:>
> On Tue, 10 Jul 2018, Daniel Harding wrote:
> 
>> On Mon, 09 Jul 2018 at 22:14:58 +0300, Johannes Schindelin wrote:
>>>
>>> On Mon, 9 Jul 2018, Daniel Harding wrote:
>>>>
>>>> On Mon, 09 Jul 2018 at 00:02:00 +0300, brian m. carlson wrote:
>>>>>
>>>>> Should this affect the "# Merge the topic branch" line (and the "# C",
>>>>> "# E", and "# H" lines in the next test) that appears below this?  It
>>>>> would seem those would qualify as comments as well.
>>>>
>>>> I intentionally did not change that behavior for two reasons:
>>>>
>>>> a) from a Git perspective, comment characters are only effectual for
>>>> comments
>>>> if they are the first character in a line
>>>>
>>>> and
>>>>
>>>> b) there are places where a '#' character from the todo list is actually
>>>> parsed and used e.g. [0] and [1].  I have not yet gotten to the point of
>>>> grokking what is going on there, so I didn't want to risk breaking
>>>> something I
>>>> didn't understand.  Perhaps Johannes could shed some light on whether the
>>>> cases you mentioned should be changed to use the configured commentChar or
>>>> not.
>>>>
>>>> [0]
>>>> https://github.com/git/git/blob/53f9a3e157dbbc901a02ac2c73346d375e24978c/sequencer.c#L2869
>>>> [1]
>>>> https://github.com/git/git/blob/53f9a3e157dbbc901a02ac2c73346d375e24978c/sequencer.c#L3797
>>>
>>> These are related. The first one tries to support
>>>
>>>   merge -C cafecafe second-branch third-branch # Octopus 2nd/3rd branch
>>>
>>> i.e. use '#' to separate between the commit(s) to merge and the oneline
>>> (the latter for the reader's pleasure, just like the onelines in the `pick
>>> <hash> <oneline>` lines.
>>>
>>> The second ensures that there is no valid label `#`.
>>>
>>> I have not really thought about the ramifications of changing this to
>>> comment_line_char, but I guess it *could* work if both locations were
>>> changed.
>>
>> Is there interest in such a change?  I'm happy to take a stab at it if there
>> is, otherwise I'll leave things as they are.
> 
> I think it would be a fine change, once we convinced ourselves that it
> does not break things (I am a little worried about this because I remember
> just how long I had to reflect about the ramifications with regards to the
> label: `#` is a valid ref name, after all, and that was the reason why I
> had to treat it specially, and I wonder whether allowing arbitrary comment
> chars will require us to add more such special handling that is not
> necessary if we stick to `#`).

Would it simpler/safer to perhaps put the oneline on its own commented 
line above?  I know it isn't quite consistent with the way onelines are 
displayed for normal commits, but it might be a worthwhile tradeoff for 
the sake of the code.  As an idea of what I am suggesting, your example 
above would become perhaps

     # Merge: Octopus 2nd/3rd branch
     merge -C cafecafe second-branch third-branch

or perhaps just

     # Octopus 2nd/3rd branch
     merge -C cafecafe second-branch third-branch

Thoughts?

> Not that the comment line char feature seems to be all that safe. I could
> imagine that setting it to ' ' (i.e. a single space) wreaks havoc with
> Git, and we have no safeguard to error out in this obviously broken case.

Technically, I think a single space might actually work with commit 
messages (at least, I can't off the top of my head think of a case where 
git would insert a non-comment line starting with a space if it wasn't 
already present in a commit message).  But if someone were actually 
crazy enough to do that I might suggest a diagnosis of "if it hurts, 
don't do that" rather than trying to equip git defend against that sort 
of thing.

Daniel Harding