checkout: Don't crash when switching away from an invalid branch.

diff --git a/builtin-diff.c b/builtin-diff.c
index 037c3039a43d198f228fbc64e46d85d4170c1329..d5fe775fc135c0905cabec6731104009ca3bfef3 100644 (file)
--- a/builtin-diff.c
+++ b/builtin-diff.c
@@ -223,7 +223,13 @@ static int builtin_diff_files(struct rev_info *revs, int argc, const char **argv
                argv++; argc--;
        }
 
-       if (revs->max_count == -1 &&
+       /*
+        * "diff --base" should not combine merges because it was not
+        * asked to.  "diff -c" should not densify (if the user wants
+        * dense one, --cc can be explicitly asked for, or just rely
+        * on the default).
+        */
+       if (revs->max_count == -1 && !revs->combine_merges &&
            (revs->diffopt.output_format & DIFF_FORMAT_PATCH))
                revs->combine_merges = revs->dense_combined_merges = 1;