Make %dirname behave like dirname (3)

Strip trailing '/' unless "/" itself
Keep "." untouched
Keep root dir for files in the root dir
Return "." for files without directory and empty strings

See man 3 dirname

Resolves: rpm-software-management#2928

rpmio/macro.c

@@ -1306,8 +1306,22 @@ static void doFoo(rpmMacroBuf mb, rpmMacroEntry me, ARGV_t argv, size_t *parsed)
 	    b++;
     } else if (rstreq("dirname", me->name)) {
 	buf = xstrdup(argv[1]);
-	if ((b = strrchr(buf, '/')) != NULL)
-	    *b = '\0';
+	if (!strcmp(buf, "")) {
+	    buf = rstrcat(&buf, ".");
+	} else {
+	    /* strip trailing / */
+	    size_t l = strlen(buf);
+	    if (l > 1 && buf[l-1] == '/')
+		buf[l-1] = '\0';
+	    if ((b = strrchr(buf, '/')) != NULL)
+		if (b == buf)
+		    /* keep root dir */
+		    buf[1] = '\0';
+		else
+		    *b = '\0';
+	    else
+		strcpy(buf, ".");
+	}
 	b = buf;
     } else if (rstreq("shrink", me->name)) {
 	/*

tests/rpmmacro.at

@@ -364,6 +364,15 @@ runroot rpm --eval "%{dirname:dir}"
 runroot rpm --eval "%{dirname dir}"
 runroot rpm --eval "%dirname"
 runroot rpm --eval "%dirname dir"
+runroot rpm --eval "%dirname /"
+runroot rpm --eval "%dirname ./"
+runroot rpm --eval "%dirname .."
+runroot rpm --eval "%dirname ../"
+runroot rpm --eval "%dirname ../foo"
+runroot rpm --eval "%dirname /foo"
+runroot rpm --eval "%dirname /foo/"
+runroot rpm --eval "%dirname /foo/foobar"
+runroot rpm --eval "%dirname /foo/foobar/"
 runroot rpm --define '%xxx /hello/%%%%/world' --eval '%{dirname:%xxx}'
 runroot rpm --eval "%{uncompress}"
 runroot rpm --eval "%{uncompress:}"
@@ -381,10 +390,19 @@ runroot rpm --eval "%shrink %%%%"
 runroot rpm --eval "%verbose foo"
 ],
 [0],
-[
-dir
-dir
-dir
+[.
+.
+.
+.
+/
+.
+.
+.
+..
+/
+/
+/foo
+/foo
 /hello/%%
 
 bar