From 88272c0fe5aca0bcdb60aeb1b4d5f4cf1c9a47b4 Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Sun, 3 Jun 2018 23:54:32 +0900
Subject: path-util: make path_make_relative() support path including dots

---
 src/basic/path-util.c     | 68 ++++++++++++++++++++++-------------------------
 src/test/test-path-util.c |  2 +-
 2 files changed, 33 insertions(+), 37 deletions(-)

diff --git a/src/basic/path-util.c b/src/basic/path-util.c
index eb91adf5b..4bca37266 100644
--- a/src/basic/path-util.c
+++ b/src/basic/path-util.c
@@ -130,8 +130,8 @@ int path_make_absolute_cwd(const char *p, char **ret) {
 
 #if 0 /// UNNEEDED by elogind
 int path_make_relative(const char *from_dir, const char *to_path, char **_r) {
-        char *r, *p;
-        unsigned n_parents;
+        char *f, *t, *r, *p;
+        unsigned n_parents = 0;
 
         assert(from_dir);
         assert(to_path);
@@ -139,85 +139,81 @@ int path_make_relative(const char *from_dir, const char *to_path, char **_r) {
 
         /* Strips the common part, and adds ".." elements as necessary. */
 
-        if (!path_is_absolute(from_dir))
+        if (!path_is_absolute(from_dir) || !path_is_absolute(to_path))
                 return -EINVAL;
 
-        if (!path_is_absolute(to_path))
-                return -EINVAL;
+        f = strdupa(from_dir);
+        t = strdupa(to_path);
+
+        path_simplify(f, true);
+        path_simplify(t, true);
 
         /* Skip the common part. */
         for (;;) {
                 size_t a, b;
 
-                from_dir += strspn(from_dir, "/");
-                to_path += strspn(to_path, "/");
+                f += *f == '/';
+                t += *t == '/';
 
-                if (!*from_dir) {
-                        if (!*to_path)
+                if (!*f) {
+                        if (!*t)
                                 /* from_dir equals to_path. */
                                 r = strdup(".");
                         else
                                 /* from_dir is a parent directory of to_path. */
-                                r = strdup(to_path);
+                                r = strdup(t);
                         if (!r)
                                 return -ENOMEM;
 
-                        path_simplify(r, false);
-
                         *_r = r;
                         return 0;
                 }
 
-                if (!*to_path)
+                if (!*t)
                         break;
 
-                a = strcspn(from_dir, "/");
-                b = strcspn(to_path, "/");
-
-                if (a != b)
-                        break;
+                a = strcspn(f, "/");
+                b = strcspn(t, "/");
 
-                if (memcmp(from_dir, to_path, a) != 0)
+                if (a != b || memcmp(f, t, a) != 0)
                         break;
 
-                from_dir += a;
-                to_path += b;
+                f += a;
+                t += b;
         }
 
         /* If we're here, then "from_dir" has one or more elements that need to
          * be replaced with "..". */
 
         /* Count the number of necessary ".." elements. */
-        for (n_parents = 0;;) {
+        for (; *f;) {
                 size_t w;
 
-                from_dir += strspn(from_dir, "/");
-
-                if (!*from_dir)
-                        break;
-
-                w = strcspn(from_dir, "/");
+                w = strcspn(f, "/");
 
                 /* If this includes ".." we can't do a simple series of "..", refuse */
-                if (w == 2 && from_dir[0] == '.' && from_dir[1] == '.')
+                if (w == 2 && f[0] == '.' && f[1] == '.')
                         return -EINVAL;
 
-                /* Count number of elements, except if they are "." */
-                if (w != 1 || from_dir[0] != '.')
-                        n_parents++;
+                /* Count number of elements */
+                n_parents++;
 
-                from_dir += w;
+                f += w;
+                f += *f == '/';
         }
 
-        r = new(char, n_parents * 3 + strlen(to_path) + 1);
+        r = new(char, n_parents * 3 + strlen(t) + 1);
         if (!r)
                 return -ENOMEM;
 
         for (p = r; n_parents > 0; n_parents--)
                 p = mempcpy(p, "../", 3);
 
-        strcpy(p, to_path);
-        path_simplify(r, false);
+        if (*t)
+                strcpy(p, t);
+        else
+                /* Remove trailing slash */
+                *(--p) = 0;
 
         *_r = r;
         return 0;
diff --git a/src/test/test-path-util.c b/src/test/test-path-util.c
index 80bca48e0..d0f7a5772 100644
--- a/src/test/test-path-util.c
+++ b/src/test/test-path-util.c
@@ -287,7 +287,7 @@ static void test_make_relative(void) {
         test("/some/path", "/", "../..");
         test("/some/path", "/some/other/path", "../other/path");
         test("/some/path/./dot", "/some/further/path", "../../further/path");
-        test("//extra/////slashes///won't////fool///anybody//", "////extra///slashes////are/just///fine///", "../../../are/just/fine");
+        test("//extra.//.//./.slashes//./won't////fo.ol///anybody//", "/././/extra././/.slashes////ar.e/.just/././.fine///", "../../../ar.e/.just/.fine");
 }
 #endif // 0
 
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