die("bug"): report bugs consistently

The vast majority of error messages in Git's source code which report a
bug use the convention to prefix the message with "BUG:".

As part of cleaning up merge-recursive to stop die()ing except in case of
detected bugs, let's just make the remainder of the bug reports consistent
with the de facto rule.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/ls-files.c

@@ -118,7 +118,8 @@ static void show_killed_files(struct dir_struct *dir)
 				 */
 				pos = cache_name_pos(ent->name, ent->len);
 				if (0 <= pos)
-					die("bug in show-killed-files");
+					die("BUG: killed-file %.*s not found",
+						ent->len, ent->name);
 				pos = -pos - 1;
 				while (pos < active_nr &&
 				       ce_stage(active_cache[pos]))

builtin/update-index.c

@@ -1146,7 +1146,7 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 		report(_("Untracked cache enabled for '%s'"), get_git_work_tree());
 		break;
 	default:
-		die("Bug: bad untracked_cache value: %d", untracked_cache);
+		die("BUG: bad untracked_cache value: %d", untracked_cache);
 	}
 
 	if (active_cache_changed) {

grep.c

@@ -693,10 +693,10 @@ static struct grep_expr *prep_header_patterns(struct grep_opt *opt)
 
 	for (p = opt->header_list; p; p = p->next) {
 		if (p->token != GREP_PATTERN_HEAD)
-			die("bug: a non-header pattern in grep header list.");
+			die("BUG: a non-header pattern in grep header list.");
 		if (p->field < GREP_HEADER_FIELD_MIN ||
 		    GREP_HEADER_FIELD_MAX <= p->field)
-			die("bug: unknown header field %d", p->field);
+			die("BUG: unknown header field %d", p->field);
 		compile_regexp(p, opt);
 	}
 
@@ -709,7 +709,7 @@ static struct grep_expr *prep_header_patterns(struct grep_opt *opt)
 
 		h = compile_pattern_atom(&pp);
 		if (!h || pp != p->next)
-			die("bug: malformed header expr");
+			die("BUG: malformed header expr");
 		if (!header_group[p->field]) {
 			header_group[p->field] = h;
 			continue;
@@ -1514,7 +1514,7 @@ static int grep_source_1(struct grep_opt *opt, struct grep_source *gs, int colle
 		case GREP_BINARY_TEXT:
 			break;
 		default:
-			die("bug: unknown binary handling mode");
+			die("BUG: unknown binary handling mode");
 		}
 	}
 

imap-send.c

@@ -511,7 +511,7 @@ static int nfsnprintf(char *buf, int blen, const char *fmt, ...)
 
 	va_start(va, fmt);
 	if (blen <= 0 || (unsigned)(ret = vsnprintf(buf, blen, fmt, va)) >= (unsigned)blen)
-		die("Fatal: buffer too small. Please report a bug.");
+		die("BUG: buffer too small. Please report a bug.");
 	va_end(va);
 	return ret;
 }

merge-recursive.c

@@ -268,7 +268,7 @@ struct tree *write_tree_from_memory(struct merge_options *o)
 				fprintf(stderr, "BUG: %d %.*s\n", ce_stage(ce),
 					(int)ce_namelen(ce), ce->name);
 		}
-		die("Bug in merge-recursive.c");
+		die("BUG: unmerged index entries in merge-recursive.c");
 	}
 
 	if (!active_cache_tree)
@@ -966,9 +966,8 @@ static struct merge_file_info merge_file_1(struct merge_options *o,
 
 			if (!oid_eq(&a->oid, &b->oid))
 				result.clean = 0;
-		} else {
-			die(_("unsupported object type in the tree"));
-		}
+		} else
+			die(_("BUG: unsupported object type in the tree"));
 	}
 
 	return result;
@@ -1354,7 +1353,7 @@ static int process_renames(struct merge_options *o,
 			const char *ren2_dst = ren2->pair->two->path;
 			enum rename_type rename_type;
 			if (strcmp(ren1_src, ren2_src) != 0)
-				die("ren1_src != ren2_src");
+				die("BUG: ren1_src != ren2_src");
 			ren2->dst_entry->processed = 1;
 			ren2->processed = 1;
 			if (strcmp(ren1_dst, ren2_dst) != 0) {
@@ -1388,7 +1387,7 @@ static int process_renames(struct merge_options *o,
 			ren2 = lookup->util;
 			ren2_dst = ren2->pair->two->path;
 			if (strcmp(ren1_dst, ren2_dst) != 0)
-				die("ren1_dst != ren2_dst");
+				die("BUG: ren1_dst != ren2_dst");
 
 			clean_merge = 0;
 			ren2->processed = 1;
@@ -1812,7 +1811,7 @@ static int process_entry(struct merge_options *o,
 		 */
 		remove_file(o, 1, path, !a_mode);
 	} else
-		die(_("Fatal merge failure, shouldn't happen."));
+		die(_("BUG: fatal merge failure, shouldn't happen."));
 
 	return clean_merge;
 }
@@ -1870,7 +1869,7 @@ int merge_trees(struct merge_options *o,
 		for (i = 0; i < entries->nr; i++) {
 			struct stage_data *e = entries->items[i].util;
 			if (!e->processed)
-				die(_("Unprocessed path??? %s"),
+				die(_("BUG: unprocessed path??? %s"),
 				    entries->items[i].string);
 		}
 

sha1_file.c

@@ -795,7 +795,7 @@ void close_all_packs(void)
 
 	for (p = packed_git; p; p = p->next)
 		if (p->do_not_close)
-			die("BUG! Want to close pack marked 'do-not-close'");
+			die("BUG: want to close pack marked 'do-not-close'");
 		else
 			close_pack(p);
 }
@@ -2330,7 +2330,7 @@ void *unpack_entry(struct packed_git *p, off_t obj_offset,
 	case OBJ_OFS_DELTA:
 	case OBJ_REF_DELTA:
 		if (data)
-			die("BUG in unpack_entry: left loop at a valid delta");
+			die("BUG: unpack_entry: left loop at a valid delta");
 		break;
 	case OBJ_COMMIT:
 	case OBJ_TREE:

trailer.c

@@ -562,7 +562,7 @@ static int git_trailer_config(const char *conf_key, const char *value, void *cb)
 			warning(_("unknown value '%s' for key '%s'"), value, conf_key);
 		break;
 	default:
-		die("internal bug in trailer.c");
+		die("BUG: trailer.c: unhandled type %d", type);
 	}
 	return 0;
 }

transport.c

@@ -566,7 +566,7 @@ void transport_take_over(struct transport *transport,
 	struct git_transport_data *data;
 
 	if (!transport->smart_options)
-		die("Bug detected: Taking over transport requires non-NULL "
+		die("BUG: taking over transport requires non-NULL "
 		    "smart_options field.");
 
 	data = xcalloc(1, sizeof(*data));

wt-status.c

@@ -263,7 +263,7 @@ static const char *wt_status_unmerged_status_string(int stagemask)
 	case 7:
 		return _("both modified:");
 	default:
-		die("bug: unhandled unmerged status %x", stagemask);
+		die("BUG: unhandled unmerged status %x", stagemask);
 	}
 }
 
@@ -388,7 +388,7 @@ static void wt_status_print_change_data(struct wt_status *s,
 	status_printf(s, color(WT_STATUS_HEADER, s), "\t");
 	what = wt_status_diff_status_string(status);
 	if (!what)
-		die("bug: unhandled diff status %c", status);
+		die("BUG: unhandled diff status %c", status);
 	len = label_width - utf8_strwidth(what);
 	assert(len >= 0);
 	if (status == DIFF_STATUS_COPIED || status == DIFF_STATUS_RENAMED)