Re: [PATCH 1/2] relative_path should honor dos_drive_prefix

Tvangeste found that the "relative_path" function could not work
properly on Windows if "in" and "prefix" have dos driver prefix.
($gmane/234434)

e.g., When execute: test-path-utils relative_path "C:/a/b" "D:/x/y",
should return "C:/a/b", but returns "../../C:/a/b", which is wrong.

So make relative_path honor dos_drive_prefix, and add test cases
for it in t0060.

Reported-by: Tvangeste <redacted>
Helped-by: Johannes Sixt [off-list ref]
Signed-off-by: Jiang Xin <redacted>
---
 path.c                | 20 ++++++++++++++++++++
 t/t0060-path-utils.sh |  4 ++++
 2 files changed, 24 insertions(+)

diff --git a/path.c b/path.c
index 7f3324a..ffcdea1 100644
--- a/path.c
+++ b/path.c

@@ -441,6 +441,16 @@ int adjust_shared_perm(const char *path)
        return 0;
 }

+static int have_same_root(const char *path1, const char *path2)
+{
+       int is_abs1, is_abs2;
+
+       is_abs1 = is_absolute_path(path1);
+       is_abs2 = is_absolute_path(path2);
+       return (is_abs1 && is_abs2 && !strncasecmp(path1, path2, 1)) ||
+              (!is_abs1 && !is_abs2);
+}
+
 /*
  * Give path as relative to prefix.
  *

@@ -461,6 +471,16 @@ const char *relative_path(const char *in, const char *prefix,
        else if (!prefix_len)
                return in;

+       if (have_same_root(in, prefix)) {
+               /* bypass dos_drive, for "c:" is identical to "C:" */
+               if (has_dos_drive_prefix(in)) {
+                       i = 2;
+                       j = 2;
+               }
+       } else {
+               return in;
+       }
+
        while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
                if (is_dir_sep(prefix[i])) {
                        while (is_dir_sep(prefix[i]))

diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index 76c7792..c3c3b33 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh

@@ -208,6 +208,10 @@ relative_path a/b/ a/b             ./
 relative_path a                a/b             ../
 relative_path x/y      a/b             ../../x/y
 relative_path a/c      a/b             ../c
+relative_path a/b      /x/y            a/b
+relative_path /a/b     x/y             /a/b    POSIX
+relative_path d:/a/b   D:/a/c          ../b    MINGW
+relative_path C:/a/b   D:/a/c          C:/a/b  MINGW
 relative_path a/b      "<empty>"       a/b
 relative_path a/b      "<null>"        a/b
 relative_path "<empty>"        /a/b            ./
--

1.8.3.rc2.14.g5ac1b82