Re: [PATCH] checkout files in-place

[Edward Thomson <ethomson@edwardthomson.com>]

On Tue, Jun 12, 2018 at 09:13:54AM +0300, Orgad Shaneh wrote:
> Some of my colleagues use an ancient version of Source Insight, which also
> locks files for write.

If that application is locking files for writing (that is to say, it did
not specify the `FILE_SHARE_WRITE` bit in the sharing modes during
`CreateFile`) then this patch would not help.

Applications, generally speaking, should be locking files for write.
It's the default in Win32 and .NET's file open APIs because few
applications are prepared to detect and support a file changing out from
underneath them in the middle of a read.

> It's less important than it was before those fixes, but it is still needed
> for users of Qt Creator 4.6 (previous versions just avoided mmap, 4.7 uses
> mmap only for system headers). Other tools on Windows might as well
> misbehave.

I don't understand what mmap'ing via `CreateFileMapping` has to do with
this.  It takes an existing `HANDLE` that was opened with `CreateFile`,
which is where the sharing mode was supplied.

I would be surprised if there are other tools on Windows that have
specified `FILE_SHARE_WRITE` but not `FILE_SHARE_DELETE`.  Generally
speaking, if you don't care about another process changing a file
underneath you then you should specify both.  If you do then you should
specify neither.

I'm not saying that git shouldn't work around a bug in QT Creator -
that's not my call, though I would be loathe to support this
configuration option in libgit2.  But I am saying that it seems like
this patch doesn't have broad applicability beyond that particular tool.

-ed