xdiff: implement empty line chunk heuristic

diff --git a/diff.c b/diff.c
index f62b7f73d8ad52205b0add37a21fd69911783b25..05ca3ce08e21082f66ea9a8c6d0b51d1e56c6815 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -25,6 +25,7 @@
 #endif
 
 static int diff_detect_rename_default;
+static int diff_compaction_heuristic = 1;
 static int diff_rename_limit_default = 400;
 static int diff_suppress_blank_empty;
 static int diff_use_color_default = -1;
@@ -183,6 +184,10 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
                diff_detect_rename_default = git_config_rename(var, value);
                return 0;
        }
+       if (!strcmp(var, "diff.compactionheuristic")) {
+               diff_compaction_heuristic = git_config_bool(var, value);
+               return 0;
+       }
        if (!strcmp(var, "diff.autorefreshindex")) {
                diff_auto_refresh_index = git_config_bool(var, value);
                return 0;
@@ -3235,6 +3240,8 @@ void diff_setup(struct diff_options *options)
        options->use_color = diff_use_color_default;
        options->detect_rename = diff_detect_rename_default;
        options->xdl_opts |= diff_algorithm;
+       if (diff_compaction_heuristic)
+               DIFF_XDL_SET(options, COMPACTION_HEURISTIC);
 
        options->orderfile = diff_order_file_cfg;
 
@@ -3712,6 +3719,10 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
                DIFF_XDL_SET(options, IGNORE_WHITESPACE_AT_EOL);
        else if (!strcmp(arg, "--ignore-blank-lines"))
                DIFF_XDL_SET(options, IGNORE_BLANK_LINES);
+       else if (!strcmp(arg, "--compaction-heuristic"))
+               DIFF_XDL_SET(options, COMPACTION_HEURISTIC);
+       else if (!strcmp(arg, "--no-compaction-heuristic"))
+               DIFF_XDL_CLR(options, COMPACTION_HEURISTIC);
        else if (!strcmp(arg, "--patience"))
                options->xdl_opts = DIFF_WITH_ALG(options, PATIENCE_DIFF);
        else if (!strcmp(arg, "--histogram"))