[PATCH 1/2] help: add help_unknown_ref

[Vikrant Varma <vikrant.varma94@gmail.com>]

Give better advice when trying to merge a branch that doesn't exist. If
the branch exists in any remotes, display a list of suggestions.

Example:
	$ git merge foo
	fatal: foo - not something we can merge

	Did you mean this?
	    bar/foo

Signed-off-by: Vikrant Varma <vikrant.varma94@gmail.com>
---
 help.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 help.h |  6 ++++++
 2 files changed, 50 insertions(+)

diff --git a/help.c b/help.c
index 02ba043..faf18b9 100644
--- a/help.c
+++ b/help.c
@@ -7,6 +7,7 @@
 #include "string-list.h"
 #include "column.h"
 #include "version.h"
+#include "refs.h"
 
 void add_cmdname(struct cmdnames *cmds, const char *name, int len)
 {
@@ -404,3 +405,46 @@ int cmd_version(int argc, const char **argv, const char *prefix)
 	printf("git version %s\n", git_version_string);
 	return 0;
 }
+
+struct similar_ref_cb {
+        const char *base_ref;
+        struct string_list similar_refs;
+};
+
+static int append_similar_ref(const char* refname, const unsigned char *sha1, int flags, void *cb_data)
+{
+        int i;
+        struct similar_ref_cb *cb = (struct similar_ref_cb *)(cb_data);
+        for (i = strlen(refname); refname[i] != '/'; i--)
+	        ;
+        /* A remote branch of the same name is deemed similar */
+        if (!prefixcmp(refname, "refs/remotes/") && !strcmp(refname + i + 1, cb->base_ref))
+	       	string_list_append(&(cb->similar_refs), refname + 13);
+        return 0;
+}
+
+void help_unknown_ref(const char* ref) {
+        int i;
+        struct similar_ref_cb ref_cb;
+        ref_cb.similar_refs = (struct string_list)STRING_LIST_INIT_NODUP;
+        ref_cb.base_ref = ref;
+
+        for_each_ref(append_similar_ref, &ref_cb);
+
+        fprintf_ln(stderr, _("fatal: %s - not something we can merge"), ref);
+
+        if (ref_cb.similar_refs.nr > 0) {
+	        fprintf_ln(stderr,
+		           Q_("\nDid you mean this?",
+		              "\nDid you mean one of these?",
+		              ref_cb.similar_refs.nr));
+
+	        for (i = 0; i < ref_cb.similar_refs.nr; i++)
+		        fprintf(stderr, "\t%s\n", ref_cb.similar_refs.items[i].string);
+        }
+        exit(1);
+}
+	
+			
+
+
diff --git a/help.h b/help.h
index 0ae5a12..613cb45 100644
--- a/help.h
+++ b/help.h
@@ -27,4 +27,10 @@ extern void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes);
 extern int is_in_cmdlist(struct cmdnames *cmds, const char *name);
 extern void list_commands(unsigned int colopts, struct cmdnames *main_cmds, struct cmdnames *other_cmds);
 
+/* 
+ * ref is not something that can be merged. Print a list of remote branches of the
+ * same name that the user might have meant. 
+ */
+extern void help_unknown_ref(const char* ref);
+
 #endif /* HELP_H */
-- 
1.8.3-rc0