help: add help_unknown_ref()

When the user gives an unknown string to a command that expects to
get a ref, we could be more helpful than just saying "that's not a
ref" and die.

Add helper function help_unknown_ref() to take care of displaying an
error message along with a list of suggested refs the user might
have meant.  An interaction with "git merge" might go like this:

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

Did you mean one of these?
origin/foo
upstream/foo

Signed-off-by: Vikrant Varma <vikrant.varma94@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/help.c b/help.c
index 02ba043319932411e90121d4147f25395782dfb5..bebfce96e637fe2444fb8bd13f69c3d9cc147dd2 100644 (file)
--- 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 +405,52 @@ 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)
+{
+       struct similar_ref_cb *cb = (struct similar_ref_cb *)(cb_data);
+       char *branch = strrchr(refname, '/') + 1;
+       /* A remote branch of the same name is deemed similar */
+       if (!prefixcmp(refname, "refs/remotes/") &&
+           !strcmp(branch, cb->base_ref))
+               string_list_append(cb->similar_refs,
+                                  refname + strlen("refs/remotes/"));
+       return 0;
+}
+
+static struct string_list guess_refs(const char *ref)
+{
+       struct similar_ref_cb ref_cb;
+       struct string_list similar_refs = STRING_LIST_INIT_NODUP;
+
+       ref_cb.base_ref = ref;
+       ref_cb.similar_refs = &similar_refs;
+       for_each_ref(append_similar_ref, &ref_cb);
+       return similar_refs;
+}
+
+void help_unknown_ref(const char *ref, const char *cmd, const char *error)
+{
+       int i;
+       struct string_list suggested_refs = guess_refs(ref);
+
+       fprintf_ln(stderr, _("%s: %s - %s"), cmd, ref, error);
+
+       if (suggested_refs.nr > 0) {
+               fprintf_ln(stderr,
+                          Q_("\nDid you mean this?",
+                             "\nDid you mean one of these?",
+                             suggested_refs.nr));
+               for (i = 0; i < suggested_refs.nr; i++)
+                       fprintf(stderr, "\t%s\n", suggested_refs.items[i].string);
+       }
+
+       string_list_clear(&suggested_refs, 0);
+       exit(1);
+}

diff --git a/help.h b/help.h
index 0ae5a124a3af9912d551caed909aac77acc59b0b..b21d7c94e8ce429ac1f58bd566c69e154d84d6a0 100644 (file)
--- a/help.h
+++ b/help.h
@@ -27,4 +27,9 @@ 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);
 
+/*
+ * call this to die(), when it is suspected that the user mistyped a
+ * ref to the command, to give suggested "correct" refs.
+ */
+extern void help_unknown_ref(const char *ref, const char *cmd, const char *error);
 #endif /* HELP_H */