Re: Regression in e02ca72: git svn rebase is broken on Windows

I tested 'relative_path' function using 'test-path-utils', and got the
following result:

    $ ./test-path-utils relative_path 'C:/a/b' 'D:/x/y'
    ../../../C:/a/b

    $ ./test-path-utils relative_path '/a/b' 'x/y'
    ../..//a/b

    $ ./test-path-utils relative_path 'a/b' '/x/y'
    ../../../a/b

For the first case, in and prefix are on different ROOT, and for the other
two cases, one path is a relative path, and another is an absolute path.

I write a patch to test whether two paths (in and prefix) have the same
root. The result after applied the patch:

    $ ./test-path-utils relative_path 'C:/a/b' 'C:/x/y'
    ../../a/b

    $ ./test-path-utils relative_path 'C:/a/b' 'D:/x/y'
    C:/a/b

    $ ./test-path-utils relative_path '/a/b' 'x/y'
    /a/b

    $ ./test-path-utils relative_path 'a/b' '/x/y'
    a/b

diff --git a/path.c b/path.c
index 7f3324a..51f5d28 100644
--- a/path.c
+++ b/path.c

@@ -441,6 +441,25 @@ int adjust_shared_perm(const char *path)
        return 0;
 }

+static int have_same_root(const char *path1, const char *path2)
+{
+       /* for POSIX:
+
+          return ((path1 && is_dir_sep(*path1)) ^
+                  (path2 && is_dir_sep(*path2))) == 0;
+       */
+       return path1 && path2 && *path1 && *path2 && (
+               (is_dir_sep(*path1) &&
+                is_dir_sep(*path2)) ||
+               (*(path1+1) == ':' &&
+                *(path2+1) == ':' &&
+                !strncasecmp(path1, path2, 1)) ||
+               (!is_dir_sep(*path1) &&
+                !is_dir_sep(*path2) &&
+                *(path1+1) != ':' &&
+                *(path2+1) != ':'));