Re: [PATCH 1/1] mingw: only test index entries for backslashes, not tree entries

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Jonathan,

On Thu, 26 Dec 2019, Jonathan Nieder wrote:

> Johannes Schindelin wrote:
> > On Thu, 26 Dec 2019, Jonathan Nieder wrote:
> >> Johannes Schindelin wrote:
>
> >>> Arguably, this is the wrong layer for that error, anyway: As long as the
> >>> user never checks out the files whose names contain backslashes, there
> >>> should not be any problem in the first place.
> [...]
> >>          between the lines of this commit messages I sense that there
> >> *are* repositories in the wild using these kinds of filenames.
> >>
> >> Can you say more about that?  What repositories are affected?  Do they
> >> contain such filenames at HEAD or only in their history?  If someone
> >> wants to check out a revision with such filenames, what should happen?
> >
> > Yes: https://github.com/zephyrproject-rtos/civetweb contains history where
> > at some stage, by mistake, a directory was called `\`. It has been fixed a
> > long time ago, but users obviously still want to be able to clone it ;-)
>
> Thanks.
>
> What should and does happen if someone tries to check out an offending
> revision?

To answer this question, I added this paragraph to the commit message:

    The idea is to prevent Git from even trying to write files with
    backslashes in their file names: while these characters are valid in
    file names on other platforms, on Windows it is interpreted as directory
    separator (which would obviously lead to ambiguities, e.g. when there is
    a file `a\b` and there is also a file `a/b`).

> [...]
> > I added this paragraph to the commit message:
> >
> >     Note: just as before, the check is guarded by `core.protectNTFS` (to
> >     allow overriding the check by toggling that config setting), and it
> >     is _only_ performed on Windows, as the backslash is not a directory
> >     separator elsewhere, even when writing to NTFS-formatted volumes.
> >
> > Does that clarify the issue enough?
>
> It helps: that tells me why the check is only performed on Windows.
>
> Since this only affects Windows, please only take this review as data
> about how someone read the patch.  The patch doesn't make non Windows
> specific code any *less* maintainable, and as a general presumption I
> assume that the Git for Windows maintainer knows best about what is
> needed for maintainability of Windows-specific code.
>
> But the commit message and docs still don't describe what the desired
> behavior is.  For example, should I be able to check out a revision
> with a backslash in it (e.g. via Git skipping the offending entry), or
> is the intended behavior for it to error out and prevent checking out
> such versions of code?

As mentioned above, the idea is to prevent Git from attempting to create
files with illegal file name characters.

> Is there anything we can or should do to prevent people checking in
> new examples of paths with backslash in them (on all platforms)?

As mentioned in my reply to Junio, I don't think that it would be wise to
even try to warn about backslashes in the file names. There are _so_ many
Git users out there, I am convinced that at least some of them have valid
use cases for file names with backslashes in them.

Ciao,
Dscho