vpick: add path_uses_vpick helper method

Add a path_uses_vpick helper method to determine if a path matches
the vpick format ('PATH/NAME.SUFFIX.v' or 'PATH.v/NAME___.SUFFIX'):

	/* good: returns 1 */
	path_uses_vpick("/var/lib/machines/mymachine.raw.v/")
	path_uses_vpick("to.v/foo___.raw

	/* bad: returns <= 0 */
	path_uses_vpick("/")
	path_uses_vpick("path/to/foo.mp4.vtt

src/shared/vpick.c

@@ -691,6 +691,41 @@ int path_pick_update_warn(
         return 1;
 }
 
+int path_uses_vpick(const char *path) {
+        _cleanup_free_ char *dir = NULL, *parent = NULL, *fname = NULL;
+        int r;
+
+        assert(path);
+
+        r = path_extract_filename(path, &fname);
+        if (r == -EADDRNOTAVAIL)
+                return 0;
+        if (r < 0)
+                return r;
+
+        /* ...PATH/NAME.SUFFIX.v */
+        if (endswith(fname, ".v"))
+                return 1;
+
+        /* ...PATH.v/NAME___.SUFFIX */
+        if (!strrstr(fname, "___"))
+                return 0;
+
+        r = path_extract_directory(path, &dir);
+        if (IN_SET(r, -EDESTADDRREQ, -EADDRNOTAVAIL)) /* only filename specified (no dir), or root or "." */
+                return 0;
+        if (r < 0)
+                return r;
+
+        r = path_extract_filename(dir, &parent);
+        if (r == -EADDRNOTAVAIL)
+                return 0;
+        if (r < 0)
+                return r;
+
+        return !!endswith(parent, ".v");
+}
+
 const PickFilter pick_filter_image_raw = {
         .type_mask = (UINT32_C(1) << DT_REG) | (UINT32_C(1) << DT_BLK),
         .architecture = _ARCHITECTURE_INVALID,

src/shared/vpick.h

@@ -57,6 +57,8 @@ int path_pick_update_warn(
                 PickFlags flags,
                 PickResult *ret);
 
+int path_uses_vpick(const char *path);
+
 extern const PickFilter pick_filter_image_raw;
 extern const PickFilter pick_filter_image_dir;
 extern const PickFilter pick_filter_image_any;

src/test/test-vpick.c

@@ -168,4 +168,27 @@ TEST(path_pick) {
         assert_se(result.architecture == ARCHITECTURE_S390);
 }
 
+TEST(path_uses_vpick) {
+        ASSERT_OK_POSITIVE(path_uses_vpick("foo.v"));
+        ASSERT_OK_POSITIVE(path_uses_vpick("path/to/foo.v"));
+        ASSERT_OK_POSITIVE(path_uses_vpick("./path/to/foo.v"));
+        ASSERT_OK_POSITIVE(path_uses_vpick("path/to.v/foo.v"));
+        ASSERT_OK_POSITIVE(path_uses_vpick("path/to/foo.raw.v"));
+        ASSERT_OK_POSITIVE(path_uses_vpick("/var/lib/machines/mymachine.raw.v/"));
+        ASSERT_OK_POSITIVE(path_uses_vpick("path/to.v/foo___.hi/a.v"));
+        ASSERT_OK_ZERO(path_uses_vpick("path/to/foo.mp4.vtt"));
+        ASSERT_OK_ZERO(path_uses_vpick("path/to/foo.mp4.v.1"));
+        ASSERT_OK_ZERO(path_uses_vpick("path/to.v/a"));
+
+        ASSERT_OK_POSITIVE(path_uses_vpick("to.v/foo___.raw"));
+        ASSERT_OK_POSITIVE(path_uses_vpick("path/to.v/foo___.raw"));
+        ASSERT_OK_ZERO(path_uses_vpick("path/to/foo___.raw"));
+        ASSERT_OK_ZERO(path_uses_vpick("path/to.v/foo__"));
+        ASSERT_OK_ZERO(path_uses_vpick("foo___.raw"));
+
+        ASSERT_LE(path_uses_vpick("/"), 0);
+        ASSERT_LE(path_uses_vpick("."), 0);
+        ASSERT_LE(path_uses_vpick(""), 0);
+}
+
 DEFINE_TEST_MAIN(LOG_DEBUG);