unit: allow extension of unit files with .d/*.conf drop-ins

For all unit files foobar.service we will now read
foobar.service.d/*.conf, too. This may be used to override certain unit
settings without having to edit unit files directly.

This makes it really easy to change specific settings for services
without having to edit any unit file:

mkdir /etc/systemd/system/avahi-daemon.service.d/
echo -e '[Service]\nNice=99' > /etc/systemd/system/avahi-daemon.service.d/nice.conf
systemctl daemon-reload

1 files changed, 10 insertions, 10 deletions

diff --git a/src/core/unit.c b/src/core/unit.c
index 45453dce6..f00cfedb8 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -1781,6 +1781,7 @@ static const char *resolve_template(Unit *u, const char *name, const char*path,
 
         assert(u);
         assert(name || path);
+        assert(p);
 
         if (!name)
                 name = path_get_file_name(path);
@@ -1795,7 +1796,8 @@ static const char *resolve_template(Unit *u, const char *name, const char*path,
         else {
                 char *i;
 
-                if (!(i = unit_name_to_prefix(u->id)))
+                i = unit_name_to_prefix(u->id);
+                if (!i)
                         return NULL;
 
                 s = unit_name_replace_instance(name, i);
@@ -1812,22 +1814,20 @@ static const char *resolve_template(Unit *u, const char *name, const char*path,
 int unit_add_dependency_by_name(Unit *u, UnitDependency d, const char *name, const char *path, bool add_reference) {
         Unit *other;
         int r;
-        char *s;
+        _cleanup_free_ char *s = NULL;
 
         assert(u);
         assert(name || path);
 
-        if (!(name = resolve_template(u, name, path, &s)))
+        name = resolve_template(u, name, path, &s);
+        if (!name)
                 return -ENOMEM;
 
-        if ((r = manager_load_unit(u->manager, name, path, NULL, &other)) < 0)
-                goto finish;
-
-        r = unit_add_dependency(u, d, other, add_reference);
+        r = manager_load_unit(u->manager, name, path, NULL, &other);
+        if (r < 0)
+                return r;
 
-finish:
-        free(s);
-        return r;
+        return unit_add_dependency(u, d, other, add_reference);
 }
 
 int unit_add_two_dependencies_by_name(Unit *u, UnitDependency d, UnitDependency e, const char *name, const char *path, bool add_reference) {