t9390: work around yet another Unix<->Win32 path issue

On Windows, there is no absolute path `/fake/path`, but MSYS2 (which Git
for Windows uses e.g. for running Bash scripts) pretends that it exists.
This only works within MSYS2 applications, of course, so... when MSYS2
sees that we hand a parameter to a non-MSYS2 application in a shell
script, it helpfully converts it to the full path (prepending MSYS2's
pseudo root directory).

Let's work around that by using a Win32-compatible path to begin with:
`$(pwd)` produces that on Windows. On other platforms, it still works.

As a bonus, this safe-guards our test against a setup where `/fake/path`
_actually exists_. Stranger things have been seen in the wild, after
all.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

t/t9390-filter-repo.sh

@@ -1291,8 +1291,9 @@ test_expect_success 'mailmap sanity checks' '
 		git clone file://"$(pwd)"/analyze_me mailmap_sanity_checks &&
 		cd mailmap_sanity_checks &&
 
-		test_must_fail git filter-repo --mailmap /fake/path 2>../err &&
-		test_i18ngrep "Cannot read /fake/path" ../err &&
+		fake=$(pwd)/fake &&
+		test_must_fail git filter-repo --mailmap "$fake"/path 2>../err &&
+		test_i18ngrep "Cannot read $fake/path" ../err &&
 
 		echo "Total Bogus" >../whoopsies &&
 		test_must_fail git filter-repo --mailmap ../whoopsies 2>../err &&