mingw: support for trailing spaces on Windows

[mika-f]

Since d2c84da (refuse to access paths with trailing spaces or periods),
git for Windows no longer handles paths containing trailing spaces and
periods. However, files with trailing spaces or periods can still be
handled correctly by the Win32 API.

For example, pass the file relative path, such as touch("abc ");, the
Win32 API will trim the trailing spaces and periods. But pass the file
absolute path, such as touch("\\\\?\\C:\\abc ");, it is possible to
treat the file correctly.

This patch allows checkout of files containing trailing spaces or
periods only if core.protectNTFS is disabled (false).
However, this patch does not change the handling of directories. This
is because the two paths will be merged or access will be refused even
if the above method is used.

Reproduction procedure:

$ git --version
git version 2.39.1.windows.1

$ git clone https://github.com/mika-sandbox/git-invalid-path-on-windows-only.git
Cloning into 'git-invalid-path-on-windows-only'...
remote: Enumerating objects: 31, done.
remote: Counting objects: 100% (31/31), done.
remote: Compressing objects: 100% (16/16), done.
remote: Total 31 (delta 3), reused 31 (delta 3), pack-reused 0
Receiving objects: 100% (31/31), done.
Resolving deltas: 100% (3/3), done.
error: invalid path 'collides-with-trailings/a.txt '
fatal: unable to checkout working tree
warning: Clone succeeded, but checkout failed.
You can inspect what was checked out with 'git status'
and retry with 'git restore --source=HEAD :/'

$ cd git-invalid-path-on-windows-only
$  fd . | as-tree
.

$ git restore --source=HEAD :/
error: invalid path 'collides-with-trailings/a.txt '
error: invalid path 'trailing-periods/d.c.'
error: invalid path 'trailing-spaces/c.rb '

$ fd . | as-tree
.
├── README.md
├── collides-with-trailings
│   ├── README.md
│   └── a.txt
├── trailing-periods
│   ├── README.md
│   └── a.txt
└── trailing-spaces
    ├── README.md
    └── b.txt

with core.protectNTFS=false before this path:

$ git clone -c core.protectNTFS=false https://github.com/mika-sandbox/git-invalid-path-on-windows-only.git
Cloning into 'git-invalid-path-on-windows-only'...
remote: Enumerating objects: 31, done.
remote: Counting objects: 100% (31/31), done.
remote: Compressing objects: 100% (16/16), done.
remote: Total 31 (delta 3), reused 31 (delta 3), pack-reused 0
Receiving objects: 100% (31/31), done.
Resolving deltas: 100% (3/3), done.
warning: the following paths have collided (e.g. case-sensitive paths
on a case-insensitive filesystem) and only one from the same
colliding group is in the working tree:

  'collides-with-trailings/a.txt '

$ cd git-invalid-path-on-windows-only
$ fd . | as-tree
.
├── README.md
├── collides-with-trailings
│   ├── README.md
│   └── a.txt
├── trailing-periods
│   ├── README.md
│   ├── a.txt
│   └── d.c <-- trimmed trailing period
└── trailing-spaces
    ├── README.md
    ├── b.txt
    └── c.rb <-- trimmed trailing space

After applying the this patch:

$ git clone https://github.com/mika-sandbox/git-invalid-path-on-windows-only.git
Cloning into 'git-invalid-path-on-windows-only'...
warning: templates not found in /mingw64/share/git-core/templates
remote: Enumerating objects: 31, done.
remote: Counting objects: 100% (31/31), done.
remote: Compressing objects: 100% (16/16), done.
remote: Total 31 (delta 3), reused 31 (delta 3), pack-reused 0
Receiving objects: 100% (31/31), done.
Resolving deltas: 100% (3/3), done.

$ cd git-invalid-path-on-windows-only
$ fd . | as-tree
.
├── README.md
├── collides-with-trailings
│   ├── README.md
│   ├── a.txt
│   └── a.txt <-- with trailing space
├── trailing-periods
│   ├── README.md
│   ├── a.txt
│   └── d.c. <-- with trailing period
└── trailing-spaces
    ├── README.md
    ├── b.txt
    └── c.rb  <-- with trailing space

For your information, other softwares and commands may trim or deny
access to files with trailing spaces or periods. For example,
PowerShell will reject such paths, but Visual Studio Code can
successfully open files with and without trailing spaces and periods.
And also, Windows Explorer displays both files with trailing spaces or
periods and files without trailing spaces or periods, and recognizes
files with trailing spaces or periods as just "File", same as non-extension.

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[dscho]

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[gitgitgadget]

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