diffcore-rename: fall back to -C when -C -C busts the rename limit

When there are too many paths in the project, the number of rename source
candidates "git diff -C -C" finds will exceed the rename detection limit,
and no inexact rename detection is performed.  We however could fall back
to "git diff -C" if the number of modified paths is sufficiently small.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 20 insertions, 1 deletions

diff --git a/builtin/diff-tree.c b/builtin/diff-tree.c
index 0d2a3e9fa..be6417d16 100644
--- a/builtin/diff-tree.c
+++ b/builtin/diff-tree.c
@@ -163,6 +163,9 @@ int cmd_diff_tree(int argc, const char **argv, const char *prefix)
 	}
 
 	if (read_stdin) {
+		int saved_nrl = 0;
+		int saved_dcctc = 0;
+
 		if (opt->diffopt.detect_rename)
 			opt->diffopt.setup |= (DIFF_SETUP_USE_SIZE_CACHE |
 					       DIFF_SETUP_USE_CACHE);
@@ -173,9 +176,16 @@ int cmd_diff_tree(int argc, const char **argv, const char *prefix)
 				fputs(line, stdout);
 				fflush(stdout);
 			}
-			else
+			else {
 				diff_tree_stdin(line);
+				if (saved_nrl < opt->diffopt.needed_rename_limit)
+					saved_nrl = opt->diffopt.needed_rename_limit;
+				if (opt->diffopt.degraded_cc_to_c)
+					saved_dcctc = 1;
+			}
 		}
+		opt->diffopt.degraded_cc_to_c = saved_dcctc;
+		opt->diffopt.needed_rename_limit = saved_nrl;
 	}
 
 	return diff_result_code(&opt->diffopt, 0);
diff --git a/builtin/log.c b/builtin/log.c
index 796e9e574..707fd5706 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -247,6 +247,8 @@ static void finish_early_output(struct rev_info *rev)
 static int cmd_log_walk(struct rev_info *rev)
 {
 	struct commit *commit;
+	int saved_nrl = 0;
+	int saved_dcctc = 0;
 
 	if (rev->early_output)
 		setup_early_output(rev);
@@ -277,7 +279,14 @@ static int cmd_log_walk(struct rev_info *rev)
 		}
 		free_commit_list(commit->parents);
 		commit->parents = NULL;
+		if (saved_nrl < rev->diffopt.needed_rename_limit)
+			saved_nrl = rev->diffopt.needed_rename_limit;
+		if (rev->diffopt.degraded_cc_to_c)
+			saved_dcctc = 1;
 	}
+	rev->diffopt.degraded_cc_to_c = saved_dcctc;
+	rev->diffopt.needed_rename_limit = saved_nrl;
+
 	if (rev->diffopt.output_format & DIFF_FORMAT_CHECKDIFF &&
 	    DIFF_OPT_TST(&rev->diffopt, CHECK_FAILED)) {
 		return 02;