git_command: pass GIT_DIR on Windows with /

When using Git under Windows, it seems that Git doesn't always parse
GIT_DIR correctly when it uses the Windows \ form, but does when it
uses / only.

For example, when using worktrees:
$ GIT_DIR='C:\Users\vapier\Desktop\repo\breakpad\tools\test\.git' git worktree list
fatal: not a git repository: ..\..\.repo\worktrees\linux-syscall-support.git\worktrees\test
$ GIT_DIR='C:/Users/vapier/Desktop/repo/breakpad/tools/test/.git' git worktree list
C:/Users/vapier/Desktop/repo/breakpad/.repo/worktrees/linux-syscall-support.git  fd00dbbd0c06 (detached HEAD)
..\..\..\..\..\src\src\third_party\lss\.git                                      fd00dbbd0c06 (detached HEAD)
..\..\..\..\..\tools\test\.git                                                   fd00dbbd0c06 (detached HEAD)

Change-Id: I666c03ae845ecb55d7f9800731ea6987d3e7f401
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/298622
Reviewed-by: Michael Mortensen <mmortensen@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/git_command.py b/git_command.py
index 8bd4e67e..d06fc77c 100644
--- a/git_command.py
+++ b/git_command.py
@@ -285,6 +285,9 @@ class GitCommand(object):
     command = [GIT]
     if bare:
       if gitdir:
+        # Git on Windows wants its paths only using / for reliability.
+        if platform_utils.isWindows():
+          gitdir = gitdir.replace('\\', '/')
         env[GIT_DIR] = gitdir
       cwd = None
     command.append(cmdv[0])