ref-filter: add an 'rstrip=<N>' option to atoms which deal with refnames

Complimenting the existing 'lstrip=<N>' option, add an 'rstrip=<N>'
option which strips `<N>` slash-separated path components from the end
of the refname (e.g., `%(refname:rstrip=2)` turns `refs/tags/foo` into
`refs`).

Signed-off-by: Karthik Nayak <Karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 39 insertions, 2 deletions

diff --git a/ref-filter.c b/ref-filter.c
index 2840ca1..47e292b 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -33,8 +33,8 @@ struct if_then_else {
 };
 
 struct refname_atom {
-	enum { R_NORMAL, R_SHORT, R_LSTRIP } option;
-	int lstrip;
+	enum { R_NORMAL, R_SHORT, R_LSTRIP, R_RSTRIP } option;
+	int lstrip, rstrip;
 };
 
 /*
@@ -95,6 +95,10 @@ static void refname_atom_parser_internal(struct refname_atom *atom,
 		atom->option = R_LSTRIP;
 		if (strtol_i(arg, 10, &atom->lstrip))
 			die(_("Integer value expected refname:lstrip=%s"), arg);
+	} else if (skip_prefix(arg, "rstrip=", &arg)) {
+		atom->option = R_RSTRIP;
+		if (strtol_i(arg, 10, &atom->rstrip))
+			die(_("Integer value expected refname:rstrip=%s"), arg);
 	} else
 		die(_("unrecognized %%(%s) argument: %s"), name, arg);
 }
@@ -1125,12 +1129,45 @@ static const char *lstrip_ref_components(const char *refname, int len)
 	return start;
 }
 
+static const char *rstrip_ref_components(const char *refname, int len)
+{
+	long remaining = len;
+	char *start = xstrdup(refname);
+
+	if (len < 0) {
+		int i;
+		const char *p = refname;
+
+		/* Find total no of '/' separated path-components */
+		for (i = 0; p[i]; p[i] == '/' ? i++ : *p++)
+			;
+		/*
+		 * The number of components we need to strip is now
+		 * the total minus the components to be left (Plus one
+		 * because we count the number of '/', but the number
+		 * of components is one more than the no of '/').
+		 */
+		remaining = i + len + 1;
+	}
+
+	while (remaining-- > 0) {
+		char *p = strrchr(start, '/');
+		if (p == NULL)
+			return "";
+		else
+			p[0] = '\0';
+	}
+	return start;
+}
+
 static const char *show_ref(struct refname_atom *atom, const char *refname)
 {
 	if (atom->option == R_SHORT)
 		return shorten_unambiguous_ref(refname, warn_ambiguous_refs);
 	else if (atom->option == R_LSTRIP)
 		return lstrip_ref_components(refname, atom->lstrip);
+	else if (atom->option == R_RSTRIP)
+		return rstrip_ref_components(refname, atom->rstrip);
 	else
 		return refname;
 }