Allow braceless variables to be expanded

(Only in environment.d files.)

We have only basic compatibility with shell syntax, but specifying variables
without using braces is probably more common, and I think a lot of people would
be surprised if this didn't work.

src/test/test-env-util.c

@@ -142,7 +142,32 @@ static void test_env_strv_get_n(void) {
                         getenv("PATH")));
 }
 
-static void test_replace_env_arg(void) {
+static void test_replace_env(bool braceless) {
+        const char *env[] = {
+                "FOO=BAR BAR",
+                "BAR=waldo",
+                NULL
+        };
+        _cleanup_free_ char *t = NULL, *s = NULL, *q = NULL, *r = NULL, *p = NULL;
+        unsigned flags = REPLACE_ENV_ALLOW_BRACELESS*braceless;
+
+        t = replace_env("FOO=$FOO=${FOO}", (char**) env, flags);
+        assert_se(streq(t, braceless ? "FOO=BAR BAR=BAR BAR" : "FOO=$FOO=BAR BAR"));
+
+        s = replace_env("BAR=$BAR=${BAR}", (char**) env, flags);
+        assert_se(streq(s, braceless ? "BAR=waldo=waldo" : "BAR=$BAR=waldo"));
+
+        q = replace_env("BARBAR=$BARBAR=${BARBAR}", (char**) env, flags);
+        assert_se(streq(q, braceless ? "BARBAR==" : "BARBAR=$BARBAR="));
+
+        q = replace_env("BAR=$BAR$BAR${BAR}${BAR}", (char**) env, flags);
+        assert_se(streq(q, braceless ? "BAR=waldowaldowaldowaldo" : "BAR=$BAR$BARwaldowaldo"));
+
+        p = replace_env("${BAR}$BAR$BAR", (char**) env, flags);
+        assert_se(streq(p, braceless ? "waldowaldowaldo" : "waldo$BAR$BAR"));
+}
+
+static void test_replace_env_argv(void) {
         const char *env[] = {
                 "FOO=BAR BAR",
                 "BAR=waldo",
@@ -256,7 +281,9 @@ int main(int argc, char *argv[]) {
         test_strv_env_set();
         test_strv_env_merge();
         test_env_strv_get_n();
-        test_replace_env_arg();
+        test_replace_env(false);
+        test_replace_env(true);
+        test_replace_env_argv();
         test_env_clean();
         test_env_name_is_valid();
         test_env_value_is_valid();

src/test/test-fileio.c

@@ -226,7 +226,10 @@ static void test_merge_env_file(void) {
                                 "twelve=${one}2\n"
                                 "twentyone=2${one}\n"
                                 "one=2\n"
-                                "twentytwo=2${one}\n", false);
+                                "twentytwo=2${one}\n"
+                                "xxx_minus_three=$xxx - 3\n"
+                                "xxx=0x$one$one$one\n"
+                                , false);
         assert(r >= 0);
 
         r = merge_env_file(&a, NULL, t);
@@ -240,8 +243,9 @@ static void test_merge_env_file(void) {
         assert_se(streq(a[1], "twelve=12"));
         assert_se(streq(a[2], "twentyone=21"));
         assert_se(streq(a[3], "twentytwo=22"));
-        assert_se(a[4] == NULL);
-
+        assert_se(streq(a[4], "xxx=0x222"));
+        assert_se(streq(a[5], "xxx_minus_three= - 3"));
+        assert_se(a[6] == NULL);
 
         r = merge_env_file(&a, NULL, t);
         assert_se(r >= 0);
@@ -254,7 +258,9 @@ static void test_merge_env_file(void) {
         assert_se(streq(a[1], "twelve=12"));
         assert_se(streq(a[2], "twentyone=21"));
         assert_se(streq(a[3], "twentytwo=22"));
-        assert_se(a[4] == NULL);
+        assert_se(streq(a[4], "xxx=0x222"));
+        assert_se(streq(a[5], "xxx_minus_three=0x222 - 3"));
+        assert_se(a[6] == NULL);
 }
 
 static void test_executable_is_script(void) {