ref-filter: move get_head_description() from branch.c

Move the implementation of get_head_description() from branch.c to
ref-filter.  This gives a description of the HEAD ref if called. This
is used as the refname for the HEAD ref whenever the
FILTER_REFS_DETACHED_HEAD option is used. Make it public because we
need it to calculate the length of the HEAD refs description in
branch.c:calc_maxwidth() when we port branch.c to use ref-filter
APIs.

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/branch.c

@@ -364,39 +364,6 @@ static void add_verbose_info(struct strbuf *out, struct ref_array_item *item,
 	strbuf_release(&subject);
 }
 
-static char *get_head_description(void)
-{
-	struct strbuf desc = STRBUF_INIT;
-	struct wt_status_state state;
-	memset(&state, 0, sizeof(state));
-	wt_status_get_state(&state, 1);
-	if (state.rebase_in_progress ||
-	    state.rebase_interactive_in_progress)
-		strbuf_addf(&desc, _("(no branch, rebasing %s)"),
-			    state.branch);
-	else if (state.bisect_in_progress)
-		strbuf_addf(&desc, _("(no branch, bisect started on %s)"),
-			    state.branch);
-	else if (state.detached_from) {
-		if (state.detached_at)
-			/* TRANSLATORS: make sure this matches
-			   "HEAD detached at " in wt-status.c */
-			strbuf_addf(&desc, _("(HEAD detached at %s)"),
-				state.detached_from);
-		else
-			/* TRANSLATORS: make sure this matches
-			   "HEAD detached from " in wt-status.c */
-			strbuf_addf(&desc, _("(HEAD detached from %s)"),
-				state.detached_from);
-	}
-	else
-		strbuf_addstr(&desc, _("(no branch)"));
-	free(state.branch);
-	free(state.onto);
-	free(state.detached_from);
-	return strbuf_detach(&desc, NULL);
-}
-
 static void format_and_print_ref_item(struct ref_array_item *item, int maxwidth,
 				      struct ref_filter *filter, const char *remote_prefix)
 {

ref-filter.c

@@ -14,6 +14,7 @@
 #include "git-compat-util.h"
 #include "version.h"
 #include "trailer.h"
+#include "wt-status.h"
 
 typedef enum { FIELD_STR, FIELD_ULONG, FIELD_TIME } cmp_type;
 typedef enum { COMPARE_EQUAL, COMPARE_UNEQUAL, COMPARE_NONE } cmp_status;
@@ -1101,6 +1102,37 @@ static void fill_remote_ref_details(struct used_atom *atom, const char *refname,
 		*s = refname;
 }
 
+char *get_head_description(void)
+{
+	struct strbuf desc = STRBUF_INIT;
+	struct wt_status_state state;
+	memset(&state, 0, sizeof(state));
+	wt_status_get_state(&state, 1);
+	if (state.rebase_in_progress ||
+	    state.rebase_interactive_in_progress)
+		strbuf_addf(&desc, _("(no branch, rebasing %s)"),
+			    state.branch);
+	else if (state.bisect_in_progress)
+		strbuf_addf(&desc, _("(no branch, bisect started on %s)"),
+			    state.branch);
+	else if (state.detached_from) {
+		/* TRANSLATORS: make sure these match _("HEAD detached at ")
+		   and _("HEAD detached from ") in wt-status.c */
+		if (state.detached_at)
+			strbuf_addf(&desc, _("(HEAD detached at %s)"),
+				state.detached_from);
+		else
+			strbuf_addf(&desc, _("(HEAD detached from %s)"),
+				state.detached_from);
+	}
+	else
+		strbuf_addstr(&desc, _("(no branch)"));
+	free(state.branch);
+	free(state.onto);
+	free(state.detached_from);
+	return strbuf_detach(&desc, NULL);
+}
+
 /*
  * Parse the object referred by ref, and grab needed value.
  */
@@ -1140,9 +1172,11 @@ static void populate_value(struct ref_array_item *ref)
 			name++;
 		}
 
-		if (starts_with(name, "refname"))
+		if (starts_with(name, "refname")) {
 			refname = ref->refname;
-		else if (starts_with(name, "symref"))
+			if (ref->kind & FILTER_REFS_DETACHED_HEAD)
+				refname = get_head_description();
+		} else if (starts_with(name, "symref"))
 			refname = ref->symref ? ref->symref : "";
 		else if (starts_with(name, "upstream")) {
 			const char *branch_name;

ref-filter.h

@@ -108,5 +108,7 @@ int parse_opt_ref_sorting(const struct option *opt, const char *arg, int unset);
 struct ref_sorting *ref_default_sorting(void);
 /*  Function to parse --merged and --no-merged options */
 int parse_opt_merge_filter(const struct option *opt, const char *arg, int unset);
+/*  Get the current HEAD's description */
+char *get_head_description(void);
 
 #endif /*  REF_FILTER_H  */