Merge branch 'jt/diff-anchored-patience'

"git diff" learned a variant of the "--patience" algorithm, to
which the user can specify which 'unique' line to be used as
anchoring points.

* jt/diff-anchored-patience:
diff: support anchoring line(s)

diff --combined diff.c
index b3ef25c3452c45227ac851dc730300d07c489bd0,9ce83e675de8d70537860498667a42904ad84f6f..516f68dbb42298d1c8bb509397f6c2eb6dfc93cb
--- 1/diff.c
--- 2/diff.c
+++ b/diff.c
@@@ -3210,6 -3210,8 +3210,8 @@@ static void builtin_diff(const char *na
                ecbdata.opt = o;
                ecbdata.header = header.len ? &header : NULL;
                xpp.flags = o->xdl_opts;
+               xpp.anchors = o->anchors;
+               xpp.anchors_nr = o->anchors_nr;
                xecfg.ctxlen = o->context;
                xecfg.interhunkctxlen = o->interhunkcontext;
                xecfg.flags = XDL_EMIT_FUNCNAMES;
@@@ -3302,6 -3304,8 +3304,8 @@@ static void builtin_diffstat(const cha
                memset(&xpp, 0, sizeof(xpp));
                memset(&xecfg, 0, sizeof(xecfg));
                xpp.flags = o->xdl_opts;
+               xpp.anchors = o->anchors;
+               xpp.anchors_nr = o->anchors_nr;
                xecfg.ctxlen = o->context;
                xecfg.interhunkctxlen = o->interhunkcontext;
                if (xdi_diff_outf(&mf1, &mf2, diffstat_consume, diffstat,
@@@ -4594,9 -4598,18 +4598,18 @@@ int diff_opt_parse(struct diff_options 
                DIFF_XDL_SET(options, INDENT_HEURISTIC);
        else if (!strcmp(arg, "--no-indent-heuristic"))
                DIFF_XDL_CLR(options, INDENT_HEURISTIC);
-       else if (!strcmp(arg, "--patience"))
+       else if (!strcmp(arg, "--patience")) {
+               int i;
                options->xdl_opts = DIFF_WITH_ALG(options, PATIENCE_DIFF);
-       else if (!strcmp(arg, "--histogram"))
+               /*
+                * Both --patience and --anchored use PATIENCE_DIFF
+                * internally, so remove any anchors previously
+                * specified.
+                */
+               for (i = 0; i < options->anchors_nr; i++)
+                       free(options->anchors[i]);
+               options->anchors_nr = 0;
+       } else if (!strcmp(arg, "--histogram"))
                options->xdl_opts = DIFF_WITH_ALG(options, HISTOGRAM_DIFF);
        else if ((argcount = parse_long_opt("diff-algorithm", av, &optarg))) {
                long value = parse_algorithm_value(optarg);
@@@ -4608,6 -4621,11 +4621,11 @@@
                options->xdl_opts &= ~XDF_DIFF_ALGORITHM_MASK;
                options->xdl_opts |= value;
                return argcount;
+       } else if (skip_prefix(arg, "--anchored=", &arg)) {
+               options->xdl_opts = DIFF_WITH_ALG(options, PATIENCE_DIFF);
+               ALLOC_GROW(options->anchors, options->anchors_nr + 1,
+                          options->anchors_alloc);
+               options->anchors[options->anchors_nr++] = xstrdup(arg);
        }
  
        /* flags options */
@@@ -5454,7 -5472,7 +5472,7 @@@ void diff_warn_rename_limit(const char 
                warning(_(rename_limit_warning));
        else
                return;
 -      if (0 < needed && needed < 32767)
 +      if (0 < needed)
                warning(_(rename_limit_advice), varname, needed);
  }