patchgit-gui: remove lines starting with the comment character

> The comment character is specified by the config variable
> 'core.commentchar'. Any lines starting with this character is considered
> a comment and should not be included in the final commit message.
>
> Teach git-gui to filter out lines in the commit message that start with
> the comment character. If the config is not set, '#' is taken as the
> default.

> Signed-off-by: Pratyush Yadav <me@yadavpratyush.com>
> ---
> diff --git a/lib/commit.tcl b/lib/commit.tcl
> @@ -209,6 +209,28 @@ You must stage at least 1 file before you can commit.
>         set msg [string trim [$ui_comm get 1.0 end]]
>         regsub -all -line {[ \t\r]+$} $msg {} msg
> +
> +       # Remove lines starting with the comment character.
> +       set comment_char [get_config core.commentchar]
> +       if {[string length $comment_char] > 1} {
> +               error_popup [mc "core.commitchar should only be one character."]
> +               unlock_index
> +               return
> +       }
> +
> +       if {$comment_char eq {}} {
> +               set comment_char "#"
> +       }
> +
> +       # If the comment character is not alphabetical, then we need to escape it
> +       # with a backslash to make sure it is not interpreted as a special character
> +       # in the regex.
> +       if {![string is alpha $comment_char]} {
> +               set comment_char "\\$comment_char"
> +       }
> +
> +       regsub -all -line "$comment_char.*(\\n|\\Z)" $msg {} msg

> On Tue, Feb 2, 2021 at 3:07 PM Pratyush Yadav <me@yadavpratyush.com> wrote:
> > The comment character is specified by the config variable
> > 'core.commentchar'. Any lines starting with this character is considered
> > a comment and should not be included in the final commit message.
> >
> > Teach git-gui to filter out lines in the commit message that start with
> > the comment character. If the config is not set, '#' is taken as the
> > default.
> 
> Thanks. This shortcoming has bugged me for a long time. A few comments below...
> 
> > Signed-off-by: Pratyush Yadav <me@yadavpratyush.com>
> > ---
> > diff --git a/lib/commit.tcl b/lib/commit.tcl
> > @@ -209,6 +209,28 @@ You must stage at least 1 file before you can commit.
> >         set msg [string trim [$ui_comm get 1.0 end]]
> >         regsub -all -line {[ \t\r]+$} $msg {} msg
> > +
> > +       # Remove lines starting with the comment character.
> > +       set comment_char [get_config core.commentchar]
> > +       if {[string length $comment_char] > 1} {
> > +               error_popup [mc "core.commitchar should only be one character."]
> > +               unlock_index
> > +               return
> > +       }
> > +
> > +       if {$comment_char eq {}} {
> > +               set comment_char "#"
> > +       }
> > +
> > +       # If the comment character is not alphabetical, then we need to escape it
> > +       # with a backslash to make sure it is not interpreted as a special character
> > +       # in the regex.
> > +       if {![string is alpha $comment_char]} {
> > +               set comment_char "\\$comment_char"
> > +       }
> > +
> > +       regsub -all -line "$comment_char.*(\\n|\\Z)" $msg {} msg
> 
> This regular expression is too loose. It will incorrectly change:
> 
>     line one
>     line # two
>     # line three
>     line four
> 
> into:
> 
>     line one
>     line
>     line four
> 
> You could fix it by anchoring the start of the match while being
> careful not to lose the newline at the start of line. Perhaps like
> this:
> 
>     regsub -all -line "(^|\\A)$comment_char.*(\\n|\\Z)" $msg {} msg

> 
> However, an even better approach than doing this manipulation manually
> might be to pass the commit message through `git stripspace
> --strip-comments` which will do the exact normalization that Git
> itself does. That way, you don't have to worry about weird corner
> cases. Also, using git-stripspace may allow you to get rid of the
> existing `trim` and `regsub` which precede the new code you added.

> The comment character is specified by the config variable
> 'core.commentchar'. Any lines starting with this character is considered
> a comment and should not be included in the final commit message.
> 
> Teach git-gui to filter out lines in the commit message that start with
> the comment character. If the config is not set, '#' is taken as the
> default.

> 
> Signed-off-by: Pratyush Yadav <me@yadavpratyush.com>
> ---
>  lib/commit.tcl | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/lib/commit.tcl b/lib/commit.tcl
> index 11379f8..3c3035f 100644
> --- a/lib/commit.tcl
> +++ b/lib/commit.tcl
> @@ -209,6 +209,28 @@ You must stage at least 1 file before you can commit.
>  	#
>  	set msg [string trim [$ui_comm get 1.0 end]]
>  	regsub -all -line {[ \t\r]+$} $msg {} msg
> +
> +	# Remove lines starting with the comment character.
> +	set comment_char [get_config core.commentchar]
> +	if {[string length $comment_char] > 1} {
> +		error_popup [mc "core.commitchar should only be one character."]
> +		unlock_index
> +		return
> +	}
> +
> +	if {$comment_char eq {}} {
> +		set comment_char "#"
> +	}
> +
> +	# If the comment character is not alphabetical, then we need to escape it
> +	# with a backslash to make sure it is not interpreted as a special character
> +	# in the regex.
> +	if {![string is alpha $comment_char]} {
> +		set comment_char "\\$comment_char"
> +	}
> +
> +	regsub -all -line "$comment_char.*(\\n|\\Z)" $msg {} msg
> +
>  	if {$msg eq {}} {
>  		error_popup [mc "Please supply a commit message.
> 

> Am 02.02.21 um 21:03 schrieb Pratyush Yadav:
> > The comment character is specified by the config variable
> > 'core.commentchar'. Any lines starting with this character is considered
> > a comment and should not be included in the final commit message.
> >
> > Teach git-gui to filter out lines in the commit message that start with
> > the comment character. If the config is not set, '#' is taken as the
> > default.
>
> This is WRONG. Git GUI is that: a GUI, it's all about WYSIWYG. If you do
> not give sufficient unambiguous visual clue to the user that certain
> lines will be ignored, you cannot ignore them.
>
> Perhaps what you are really only interested in is to remove the list of
> conflicted files after a merge conflict? Then the correct way to proceed
> would be to sanitize the contents of .git/MERGE_MSG before it is
> inserted into the edit box.

> So, perhaps one way forward is for Pratyush to emulate that behavior
> and insert some text into the edit box saying "lines beginning with
> '#' will be ignored", or add a label above or below the edit box
> stating the same. (Of course, the actual displayed comment-character
> should be determined dynamically.)

> On Wed, Feb 3, 2021 at 12:48 PM Eric Sunshine <sunshine@sunshineco.com> wrote:
>> So, perhaps one way forward is for Pratyush to emulate that behavior
>> and insert some text into the edit box saying "lines beginning with
>> '#' will be ignored", or add a label above or below the edit box
>> stating the same. (Of course, the actual displayed comment-character
>> should be determined dynamically.)
> 
> Even more fancy would be to add a checkbox below the edit field which
> both enables/disables the "stripspace" behavior and allows the user to
> specify the comment-character. For instance:
> 
>     [x] ignore lines beginning with [#]
> 
> where [x] is the checkbox and [#] is a text field in which the user
> can type the comment-character.
> 
> For convenience, the checkbox would be checked by default, and the
> comment-character would default to the user's configured
> comment-character or "#".

> On Wed, Feb 3, 2021 at 12:35 PM Johannes Sixt <j6t@kdbg.org> wrote:
> > Am 02.02.21 um 21:03 schrieb Pratyush Yadav:
> > > The comment character is specified by the config variable
> > > 'core.commentchar'. Any lines starting with this character is considered
> > > a comment and should not be included in the final commit message.
> > >
> > > Teach git-gui to filter out lines in the commit message that start with
> > > the comment character. If the config is not set, '#' is taken as the
> > > default.
> >
> > This is WRONG. Git GUI is that: a GUI, it's all about WYSIWYG. If you do
> > not give sufficient unambiguous visual clue to the user that certain
> > lines will be ignored, you cannot ignore them.
> >
> > Perhaps what you are really only interested in is to remove the list of
> > conflicted files after a merge conflict? Then the correct way to proceed
> > would be to sanitize the contents of .git/MERGE_MSG before it is
> > inserted into the edit box.

> 
> This is indeed the case I run into which is annoying because the
> commented-out list of conflicted files does not get removed when
> git-gui performs the actual commit.
> 
> However, although what you propose here seems superficially enticing,
> it doesn't mirror the behavior of git-commit itself when launching an
> editor, in which case the unsanitized file (containing the
> commented-out conflicted file list) is loaded into the editor
> verbatim, and it is only sanitized when the edit session is finished.
> The important difference is that extra text is added to the edit
> buffer telling the user explicitly that "lines beginning with '#' will
> be ignored".

> So, perhaps one way forward is for Pratyush to emulate that behavior
> and insert some text into the edit box saying "lines beginning with
> '#' will be ignored", or add a label above or below the edit box
> stating the same. (Of course, the actual displayed comment-character
> should be determined dynamically.)