[PATCH/RFC 1/4] cleanup_path: force forward slashes on Windows

From: Delilah Ashley Wu <delilahwu@microsoft.com>

Git prefers forward slashes as directory separators across all platforms. On Windows, the backslash is the native directory separator, but all Windows versions supported by Git also accept the forward slash in all but rare circumstances. Our tests expect forward slashes. Git generates relative paths with forward slashes. Forward slashes are more convenient to use in shell scripts.

For these reasons, we enforced forward slashes in `interpolate_path()` in 5ca6b7bb47b (config --show-origin: report paths with forward slashes, 2016-03-23). However, other code paths may generate paths containing backslashes. For example, `config --show-origin` prints the XDG config path with mixed slashes on Windows:

$ git config --list --show-origin file:C:/Program Files/Git/etc/gitconfig system.foo=bar file:"C:\\Users\\delilah/.config/git/config" xdg.foo=bar file:C:/Users/delilah/.gitconfig home.foo=bar file:.git/config local.foo=bar

Let's enforce forward slashes in all code paths that directly or indirectly call `cleanup_path()` by modifying it to use `convert_slashes()` on Windows. Since `convert_slashes()` modifies the path in-place, change the argument and return type of `cleanup_path()` from `const char *` to `char *`. All existing callers of `cleanup_path()` pass `char *` anyways, so this change is compatible.

The next patch, config: test home and xdg files in `list --global`, will assert that the XDG config path uses forward slashes.

Suggested-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Delilah Ashley Wu <delilahwu@microsoft.com>
Reviewed-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 path.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)