Jeff King <p...@peff.net> writes:

> We've already released a version with --compaction-heuristic, so we are
> stuck keeping it forever either way.

While I do not necessarily agree with this conclusion (we've already
released it labelled as experimental; can't we freely take it
away?), that may be of lessor impact.  I like it better.

If it involves renaming and swapping, however, we may be talking
about a change that we cannot deliver with confidence in less than a
week before -rc1, which sounds, eh, suboptimal.

FWIW, here is how the removal of compaction without renaming looks
like.

 Documentation/diff-heuristic-options.txt |  2 --
 builtin/blame.c                          |  3 +--
 diff.c                                   | 23 +++--------------------
 git-add--interactive.perl                |  3 ---
 xdiff/xdiff.h                            |  3 +--
 xdiff/xdiffi.c                           | 15 ---------------
 6 files changed, 5 insertions(+), 44 deletions(-)

diff --git a/Documentation/diff-heuristic-options.txt 
b/Documentation/diff-heuristic-options.txt
index 36cb549df9..d4f3d95505 100644
--- a/Documentation/diff-heuristic-options.txt
+++ b/Documentation/diff-heuristic-options.txt
@@ -1,7 +1,5 @@
 --indent-heuristic::
 --no-indent-heuristic::
---compaction-heuristic::
---no-compaction-heuristic::
        These are to help debugging and tuning experimental heuristics
        (which are off by default) that shift diff hunk boundaries to
        make patches easier to read.
diff --git a/builtin/blame.c b/builtin/blame.c
index 4ddfadb71f..f45416a6c3 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -2597,7 +2597,6 @@ int cmd_blame(int argc, const char **argv, const char 
*prefix)
                 * output:
                 */
                { OPTION_LOWLEVEL_CALLBACK, 0, "indent-heuristic", NULL, NULL, 
N_("Use an experimental indent-based heuristic to improve diffs"), 
PARSE_OPT_NOARG, parse_opt_unknown_cb },
-               { OPTION_LOWLEVEL_CALLBACK, 0, "compaction-heuristic", NULL, 
NULL, N_("Use an experimental blank-line-based heuristic to improve diffs"), 
PARSE_OPT_NOARG, parse_opt_unknown_cb },
 
                OPT_BIT(0, "minimal", &xdl_opts, N_("Spend extra cycles to find 
better match"), XDF_NEED_MINIMAL),
                OPT_STRING('S', NULL, &revs_file, N_("file"), N_("Use revisions 
from <file> instead of calling git-rev-list")),
@@ -2645,7 +2644,7 @@ int cmd_blame(int argc, const char **argv, const char 
*prefix)
        }
 parse_done:
        no_whole_file_rename = !DIFF_OPT_TST(&revs.diffopt, FOLLOW_RENAMES);
-       xdl_opts |= revs.diffopt.xdl_opts & (XDF_COMPACTION_HEURISTIC | 
XDF_INDENT_HEURISTIC);
+       xdl_opts |= revs.diffopt.xdl_opts & XDF_INDENT_HEURISTIC;
        DIFF_OPT_CLR(&revs.diffopt, FOLLOW_RENAMES);
        argc = parse_options_end(&ctx);
 
diff --git a/diff.c b/diff.c
index 8981477c43..741ce8c68d 100644
--- a/diff.c
+++ b/diff.c
@@ -28,7 +28,6 @@
 
 static int diff_detect_rename_default;
 static int diff_indent_heuristic; /* experimental */
-static int diff_compaction_heuristic; /* experimental */
 static int diff_rename_limit_default = 400;
 static int diff_suppress_blank_empty;
 static int diff_use_color_default = -1;
@@ -223,16 +222,8 @@ void init_diff_ui_defaults(void)
 
 int git_diff_heuristic_config(const char *var, const char *value, void *cb)
 {
-       if (!strcmp(var, "diff.indentheuristic")) {
+       if (!strcmp(var, "diff.indentheuristic"))
                diff_indent_heuristic = git_config_bool(var, value);
-               if (diff_indent_heuristic)
-                       diff_compaction_heuristic = 0;
-       }
-       if (!strcmp(var, "diff.compactionheuristic")) {
-               diff_compaction_heuristic = git_config_bool(var, value);
-               if (diff_compaction_heuristic)
-                       diff_indent_heuristic = 0;
-       }
        return 0;
 }
 
@@ -3380,8 +3371,6 @@ void diff_setup(struct diff_options *options)
        options->xdl_opts |= diff_algorithm;
        if (diff_indent_heuristic)
                DIFF_XDL_SET(options, INDENT_HEURISTIC);
-       else if (diff_compaction_heuristic)
-               DIFF_XDL_SET(options, COMPACTION_HEURISTIC);
 
        options->orderfile = diff_order_file_cfg;
 
@@ -3876,16 +3865,10 @@ int diff_opt_parse(struct diff_options *options,
                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, "--indent-heuristic")) {
+       else if (!strcmp(arg, "--indent-heuristic"))
                DIFF_XDL_SET(options, INDENT_HEURISTIC);
-               DIFF_XDL_CLR(options, COMPACTION_HEURISTIC);
-       } else if (!strcmp(arg, "--no-indent-heuristic"))
-               DIFF_XDL_CLR(options, INDENT_HEURISTIC);
-       else if (!strcmp(arg, "--compaction-heuristic")) {
-               DIFF_XDL_SET(options, COMPACTION_HEURISTIC);
+       else if (!strcmp(arg, "--no-indent-heuristic"))
                DIFF_XDL_CLR(options, INDENT_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"))
diff --git a/git-add--interactive.perl b/git-add--interactive.perl
index ee3d812695..5a55d80b9d 100755
--- a/git-add--interactive.perl
+++ b/git-add--interactive.perl
@@ -46,7 +46,6 @@
 
 my $diff_algorithm = $repo->config('diff.algorithm');
 my $diff_indent_heuristic = $repo->config_bool('diff.indentheuristic');
-my $diff_compaction_heuristic = $repo->config_bool('diff.compactionheuristic');
 my $diff_filter = $repo->config('interactive.difffilter');
 
 my $use_readkey = 0;
@@ -753,8 +752,6 @@ sub parse_diff {
        }
        if ($diff_indent_heuristic) {
                splice @diff_cmd, 1, 0, "--indent-heuristic";
-       } elsif ($diff_compaction_heuristic) {
-               splice @diff_cmd, 1, 0, "--compaction-heuristic";
        }
        if (defined $patch_mode_revision) {
                push @diff_cmd, get_diff_reference($patch_mode_revision);
diff --git a/xdiff/xdiff.h b/xdiff/xdiff.h
index 8db16d4ae6..b090ad8eac 100644
--- a/xdiff/xdiff.h
+++ b/xdiff/xdiff.h
@@ -41,8 +41,7 @@ extern "C" {
 
 #define XDF_IGNORE_BLANK_LINES (1 << 7)
 
-#define XDF_COMPACTION_HEURISTIC (1 << 8)
-#define XDF_INDENT_HEURISTIC (1 << 9)
+#define XDF_INDENT_HEURISTIC (1 << 8)
 
 #define XDL_EMIT_FUNCNAMES (1 << 0)
 #define XDL_EMIT_FUNCCONTEXT (1 << 2)
diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c
index 760fbb6db7..f9be87fdfb 100644
--- a/xdiff/xdiffi.c
+++ b/xdiff/xdiffi.c
@@ -906,21 +906,6 @@ int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long 
flags) {
                                if (group_previous(xdfo, &go))
                                        xdl_bug("group sync broken sliding to 
match");
                        }
-               } else if ((flags & XDF_COMPACTION_HEURISTIC) && blank_lines) {
-                       /*
-                        * Compaction heuristic: if it is possible to shift the
-                        * group to make its bottom line a blank line, do so.
-                        *
-                        * As we already shifted the group forward as far as
-                        * possible in the earlier loop, we only need to handle
-                        * backward shifts, not forward ones.
-                        */
-                       while (!is_blank_line(xdf->recs[g.end - 1], flags)) {
-                               if (group_slide_up(xdf, &g, flags))
-                                       xdl_bug("blank line disappeared");
-                               if (group_previous(xdfo, &go))
-                                       xdl_bug("group sync broken sliding to 
blank line");
-                       }
                } else if (flags & XDF_INDENT_HEURISTIC) {
                        /*
                         * Indent heuristic: a group of pure add/delete lines

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