Re: [PATCH] t9001-send-email.sh: fix expected absolute paths on Windows

Hi Hannes,

On Mon, 24 May 2021, Johannes Sixt wrote:

Git for Windows is a native Windows program that works with native
absolute paths in the drive letter style C:\dir. The auxiliary
infrastructure is based on MSYS2, which uses POSIX style /C/dir.

As far as I remember, VMS is also POSIX, and it has a different path
style. Therefore I would probably use the term "Unix style" here instead
of "POSIX style".

But that has nothing to do with the validity of your point: it is still
a correct and important observation.

When we test for output of absolute paths produced by git.exe, we
usally have to expect C:\dir style paths. To produce such expected
paths, we have to use $(pwd) in the test scripts; the alternative,
$PWD, produces a POSIX style path. ($PWD is a shell variable, and the
shell is bash, an MSYS2 program, and operates in the POSIX realm.)

There are two recently added tests that were written to expect C:\dir
paths. The output that is tested is produced by `git send-email`, but
behind the scenes, this is a Perl script, which also works in the
POSIX realm and produces /C/dir style output.

In the first test case that is changed here, replace $(pwd) by $PWD
so that the expected path is constructed using /C/dir style.

The second test case sets core.hooksPath to an absolute path. Since
the test script talks to native git.exe, it is supposed to place a
C:/dir style path into the configuration; therefore, keep $(pwd).
When this configuration value is consumed by the Perl script, it is
transformed to /C/dir style by the MSYS2 layer and echoed back in
this form in the error message. Hence, do use $PWD for the expected
value.

Signed-off-by: Johannes Sixt <redacted>
---
 When I say "the configuration is transformed to /C/dir style", I am
 actually hand-waving: I can observe that a transformation must
 happen somewhere, but I actually do not know where the conversion
 really happens. "The MSYS2 layer" is my best qualified guess.

Indeed, it is the MSYS2 runtime that performs this conversion. Concretely,
whenever you call a non-MSYS2 program from within MSYS2, command-line
arguments that look like Unix paths are converted by replacing forward
slashes with backslashes and by prefixing absolute paths with MSYS2' root
directory (as a Windows style path, of course).

However, in this instance, it is a different problem, I think.

Perl cannot handle Windows style paths. At least _Git's_ Perl scripts
cannot.

For example, the `PATH` variable is assumed to contain colon-separated
directory paths in our scripts. But that is not true on Windows: the colon
already separates the drive letter from the rest of the path, and
therefore the separator used in `PATH` is a _semicolon_.

To help with this, the MSYS2 runtime converts the command-line arguments
and environment variables that look like path lists (such as `PATH`) and
paths (such as `SYSTEMROOT`) from Windows style to Unix style when it
detects that, say, MSYS2's Perl is started from a non-MSYS2 program such
as `git.exe`.

Which means that the Perl code executed in Ævar's tests spits out Unix
style paths.

Happily for us, the MSYS2 Bash with which Git's test suite is expected to
be executed on Windows understands those Unix style paths very well! All
we need to do is to use them here, and that is what your patch does,
therefore:

Acked-by: Johannes Schindelin <redacted>

Thank you,
Dscho