From 7ddc01a5e03ccb068382aa1df9934591ec9824fb Mon Sep 17 00:00:00 2001
From: Franck Bui <fbui@suse.com>
Date: Mon, 4 Dec 2017 11:36:17 +0100
Subject: [PATCH 1/3] delta: check if a prefix needs to be skipped only once

The condition is already tested later by process_fix() therefore there's no
need the check in process_suffix_chop() since it will end up calling
process_fix() anyways.
---
 src/delta/delta.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/src/delta/delta.c b/src/delta/delta.c
index d286881698..f626537438 100644
--- a/src/delta/delta.c
+++ b/src/delta/delta.c
@@ -520,13 +520,6 @@ static int process_suffix_chop(const char *arg) {
         /* Strip prefix from the suffix */
         NULSTR_FOREACH(p, prefixes) {
                 const char *suffix;
-                int skip;
-
-                skip = should_skip_prefix(p);
-                if (skip < 0)
-                        return skip;
-                if (skip)
-                        continue;
 
                 suffix = startswith(arg, p);
                 if (suffix) {

From 4cc893e742d0e4f0e29f383f0a29f44ef0a2e7b8 Mon Sep 17 00:00:00 2001
From: Franck Bui <fbui@suse.com>
Date: Mon, 4 Dec 2017 09:36:22 +0100
Subject: [PATCH 2/3] delta: extend skip logic to work on full directory paths
 (prefix+suffix)

Rather than only checking that a prefix path is a symlink to another prefix
path (this can happen with split-usr=true and /lib a symlink to /usr/lib),
extend the logic in should_skip_prefix() so that the check is done on the full
directory path (prefix + suffix).

This allows to catch such cases as well:

 # ls -ld /lib /lib/udev
 drwxr-xr-x 1 root root 86 Nov 22 13:14 /lib
 lrwxrwxrwx 1 root root 13 Sep  4 17:47 /lib/udev -> /usr/lib/udev

where prefix=/lib and suffix=udev/rules.d
---
 src/delta/delta.c | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/src/delta/delta.c b/src/delta/delta.c
index f626537438..6d99d75d3d 100644
--- a/src/delta/delta.c
+++ b/src/delta/delta.c
@@ -392,19 +392,28 @@ static int enumerate_dir(
         return 0;
 }
 
-static int should_skip_prefix(const char* p) {
+static bool should_skip_path(const char *prefix, const char *suffix) {
 #if HAVE_SPLIT_USR
-        int r;
         _cleanup_free_ char *target = NULL;
+        const char *p;
+        char *dirname;
 
-        r = chase_symlinks(p, NULL, 0, &target);
-        if (r < 0)
-                return r;
+        dirname = strjoina(prefix, "/", suffix);
 
-        return !streq(p, target) && nulstr_contains(prefixes, target);
-#else
-        return 0;
+        if (chase_symlinks(dirname, NULL, 0, &target) < 0)
+                return false;
+
+        NULSTR_FOREACH(p, prefixes) {
+                if (path_startswith(dirname, p))
+                        continue;
+
+                if (path_equal(target, strjoina(p, "/", suffix))) {
+                        log_debug("%s redirects to %s, skipping.", dirname, target);
+                        return true;
+                }
+        }
 #endif
+        return false;
 }
 
 static int process_suffix(const char *suffix, const char *onlyprefix) {
@@ -434,14 +443,8 @@ static int process_suffix(const char *suffix, const char *onlyprefix) {
 
         NULSTR_FOREACH(p, prefixes) {
                 _cleanup_free_ char *t = NULL;
-                int skip;
 
-                skip = should_skip_prefix(p);
-                if (skip < 0) {
-                        r = skip;
-                        goto finish;
-                }
-                if (skip)
+                if (should_skip_path(p, suffix))
                         continue;
 
                 t = strjoin(p, "/", suffix);

From a9d041fa47bed53cc324462726af20007a72ad27 Mon Sep 17 00:00:00 2001
From: Franck Bui <fbui@suse.com>
Date: Thu, 7 Dec 2017 21:17:56 +0100
Subject: [PATCH 3/3] delta: don't ignore PREFIX when the given argument is
 PREFIX/SUFFIX
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Before this patch, when systemd-delta was asked for overwritten configuration
files in a directory specified by PREFIX/SUFFIX, it ignored the given PREFIX
and listed all overwritten files matching the subdirectory specified by
SUFFIX. Hence we could get the following:

  $ ./build/systemd-delta /usr/local/lib/systemd/system
  [REDIRECTED] /etc/systemd/system/default.target → /usr/lib/systemd/system/default.target
  [EXTENDED]   /usr/lib/systemd/system/systemd-sysctl.service → /usr/lib/systemd/system/systemd-sysctl.service.d/50-kernel-uname_r.conf

systemd-delta showed overwritten configuration files in /usr/lib whereas only
overwritten ones in /usr/local/lib should have been reported (none in my case).

With the patch applied, we now get:

  $ ./build/systemd-delta /usr/local/lib/systemd/system
  0 overridden configuration files found.
---
 src/delta/delta.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/delta/delta.c b/src/delta/delta.c
index 6d99d75d3d..9c8841d46d 100644
--- a/src/delta/delta.c
+++ b/src/delta/delta.c
@@ -528,7 +528,7 @@ static int process_suffix_chop(const char *arg) {
                 if (suffix) {
                         suffix += strspn(suffix, "/");
                         if (*suffix)
-                                return process_suffix(suffix, NULL);
+                                return process_suffix(suffix, p);
                         else
                                 return process_suffixes(arg);
                 }