bug#68377: Cannot commit parts of *vc-diff* on Microsoft Windows

[Dmitry Gutov]

On 11/01/2024 14:28, Eli Zaretskii wrote:
> > From: Sam Steingold <sds@gnu.org>
> > Date: Wed, 10 Jan 2024 21:07:14 -0500
> >
> > https://emacs.stackexchange.com/q/80039/795
> >
> > Emacs has a beautiful feature: in the `*vc-diff*` buffer (generated by 
> > [`vc-diff`](https://www.gnu.org/software/emacs/manual/html_node/emacs/Old-Revisions.html) either by <kbd>C-x v 
> > =</kbd> in a file buffer or by <kbd>=</kbd> in a `*vc-dir*` buffer), kill unwanted hunks with 
> > <kbd>k</kbd> (i.e., [`diff-hunk-kill`](https://www.gnu.org/software/emacs/manual/html_node/emacs/Diff-Mode.html)) 
> > and then commit the remaining hunks with <kbd>C-x v v</kbd> (i.e., 
> > [`vc-next-action`](https://www.gnu.org/software/emacs/manual/html_node/emacs/Basic-VC-Editing.html)). If you don't know about 
> > it -- try it, it is incredibly useful!
>
> (I must say that formatting of this report is AWFUL!  How can a human
> being be expected to read and understand it it??  PLEASE try to make
> bug reports more readable in the future.)

Looked fine to me.

I think the Markdown format is very readable.

> > Alas, it does _not_ work for me on windows: after <kbd>C-c C-c</kbd> (i.e., 
> > [`log-edit-done`](https://www.gnu.org/software/emacs/manual/html_node/emacs/Log-Buffer.html))
> >  in `*vc-log*`, I get
> > > vc-do-command: Failed (status 1): 
> > > c:/Users/ssteingold/AppData/Local/Git/bin/git.exe --no-pager apply --cached 
> > > c:/msys64/tmp/git-patchPbbWgJ
> >
> > and `*vc*` buffer is
> > ```
> > error: patch failed: fxpy/model.py:1071
> > error: fxpy/model.py: patch does not apply
> > ```
> >
> > ***Additionally***:
> >
> > 1. Software:
> >     * [`GNU Emacs 29.1 (build 2, x86_64-w64-mingw32) of 
> > 2023-08-02`](https://ftp.gnu.org/gnu/emacs/windows/emacs-29/)
> >     * [`git version 2.42.0.windows.2`](https://gitforwindows.org/)
> > 1. *normal* commits work just **fine**, using `vc-next-action` from either file 
> > buffer or `*vc-dir*`.
> > 1. All my files have unix line terminators (`LF`) as indicated in the mode line 
> > as `(Unix)`
> > 1. I set `autocrlf` to `false` globally
> > 1. I have `(prefer-coding-system 'utf-8-unix)` in `.emacs`
> > 1. `vc-coding-system-inherit-eol` is `t`, I did not touch it
> > 1. When I add `"-v"` to `git apply` invocation in `vc-git-checkin` 
> > (`vc-git.el`), `*vc*` buffer contains `error: while searching for:.....` and every line 
> > in `.....` is terminated with `?` - which seems to indicate line-ending problems... (!!!)
> >
> > ***Q***: how do I fix this?
> > (This is a work box, I cannot send email from Emacs, so I cannot even file an 
> > Emacs bug report!)
> >
> > # work-around 1
> >
> > Add
> > ```
> > (setq coding-system-for-write 'utf-8-unix)
> > ```
> > inside `(with-temp-file patch-file ...)` in `vc-git-checkin`
>
> The code in question already does:
>
>          (let ((patch-file (make-nearby-temp-file "git-patch"))
>                ;; Temporarily countermand the let-binding at the
>                ;; beginning of this function.
>                (coding-system-for-write
>                 (coding-system-change-eol-conversion
>                  ;; On DOS/Windows, it is important for the patch file
>                  ;; to have the Unix EOL format, because Git expects
>                  ;; that, even on Windows.
>                  (or pcsw vc-git-commits-coding-system) 'unix)))
>            (with-temp-file patch-file
>              (insert vc-git-patch-string))
>
> So coding-system-for-write should already be -unix when with-temp-file
> runs.  I guess there's more here than meets the eye, or maybe I'm
> missing something.

I think this is the same as bug#65049, meaning that it's fixed on 
master, but not in Emacs 29.1 (which was the version specified in the 
report).