1 files changed, 90 insertions, 1 deletions

diff --git a/rebase-interactive.c b/rebase-interactive.c
index 842fa07e7e..dfa6dd530f 100644
--- a/rebase-interactive.c
+++ b/rebase-interactive.c
@@ -1,8 +1,32 @@
 #include "cache.h"
 #include "commit.h"
-#include "rebase-interactive.h"
 #include "sequencer.h"
+#include "rebase-interactive.h"
 #include "strbuf.h"
+#include "commit-slab.h"
+#include "config.h"
+
+enum missing_commit_check_level {
+	MISSING_COMMIT_CHECK_IGNORE = 0,
+	MISSING_COMMIT_CHECK_WARN,
+	MISSING_COMMIT_CHECK_ERROR
+};
+
+static enum missing_commit_check_level get_missing_commit_check_level(void)
+{
+	const char *value;
+
+	if (git_config_get_value("rebase.missingcommitscheck", &value) ||
+			!strcasecmp("ignore", value))
+		return MISSING_COMMIT_CHECK_IGNORE;
+	if (!strcasecmp("warn", value))
+		return MISSING_COMMIT_CHECK_WARN;
+	if (!strcasecmp("error", value))
+		return MISSING_COMMIT_CHECK_ERROR;
+	warning(_("unrecognized setting %s for option "
+		  "rebase.missingCommitsCheck. Ignoring."), value);
+	return MISSING_COMMIT_CHECK_IGNORE;
+}
 
 void append_todo_help(unsigned edit_todo, unsigned keep_empty,
 		      struct strbuf *buf)
@@ -89,3 +113,68 @@ int edit_todo_list(struct repository *r, unsigned flags)
 
 	return 0;
 }
+
+define_commit_slab(commit_seen, unsigned char);
+/*
+ * Check if the user dropped some commits by mistake
+ * Behaviour determined by rebase.missingCommitsCheck.
+ * Check if there is an unrecognized command or a
+ * bad SHA-1 in a command.
+ */
+int todo_list_check(struct todo_list *old_todo, struct todo_list *new_todo)
+{
+	enum missing_commit_check_level check_level = get_missing_commit_check_level();
+	struct strbuf missing = STRBUF_INIT;
+	int res = 0, i;
+	struct commit_seen commit_seen;
+
+	init_commit_seen(&commit_seen);
+
+	if (check_level == MISSING_COMMIT_CHECK_IGNORE)
+		goto leave_check;
+
+	/* Mark the commits in git-rebase-todo as seen */
+	for (i = 0; i < new_todo->nr; i++) {
+		struct commit *commit = new_todo->items[i].commit;
+		if (commit)
+			*commit_seen_at(&commit_seen, commit) = 1;
+	}
+
+	/* Find commits in git-rebase-todo.backup yet unseen */
+	for (i = old_todo->nr - 1; i >= 0; i--) {
+		struct todo_item *item = old_todo->items + i;
+		struct commit *commit = item->commit;
+		if (commit && !*commit_seen_at(&commit_seen, commit)) {
+			strbuf_addf(&missing, " - %s %.*s\n",
+				    find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV),
+				    item->arg_len,
+				    todo_item_get_arg(old_todo, item));
+			*commit_seen_at(&commit_seen, commit) = 1;
+		}
+	}
+
+	/* Warn about missing commits */
+	if (!missing.len)
+		goto leave_check;
+
+	if (check_level == MISSING_COMMIT_CHECK_ERROR)
+		res = 1;
+
+	fprintf(stderr,
+		_("Warning: some commits may have been dropped accidentally.\n"
+		"Dropped commits (newer to older):\n"));
+
+	/* Make the list user-friendly and display */
+	fputs(missing.buf, stderr);
+	strbuf_release(&missing);
+
+	fprintf(stderr, _("To avoid this message, use \"drop\" to "
+		"explicitly remove a commit.\n\n"
+		"Use 'git config rebase.missingCommitsCheck' to change "
+		"the level of warnings.\n"
+		"The possible behaviours are: ignore, warn, error.\n\n"));
+
+leave_check:
+	clear_commit_seen(&commit_seen);
+	return res;
+}