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		./