log: improve --follow following renames for non-linear history
Have a repo with a subtree merge, do a 'git log --follow prefix/test.c', the output only contains history in the outer repo, not commits that were merged via a subtree merge. What happens is that 'git log --follow' stores the followed path only in opt->diffopt.pathspec, so in case the commit history is non-linear, and multiple parents have renames to the followed path, then the end result isn't really defined: the first commit that happens to be visited in one of the parents update opt->diffopt.pathspec, and from that point, only that updated path is visited. Fix the problem by introducing a commit -> path map (follow_pathspec_slab) that stores what will be a path to follow when visiting that parent. At the top of log_tree_commit(), if the slab has an entry for this commit, we replace opt->diffopt.pathspec with a path from this entry, so the correct path is followed, even if an unrelated sub-tree changed the path to be followed to something else. After log_tree_diff() runs, we record each parent's path in the slab. As a result, the walk order doesn't matter, which was exactly the source of problems previously. This helps with subtree merges (rename happens inside the merge commit), but also fixes the general case when the rename happens in the history of parents, not in the merge commit itself. Signed-off-by: Miklos Vajna <vmiklos@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Miklos Vajna committed
Jun 22, 2026 at 08:23 UTC
304812ed33dec7ea7e68928feab38199d796ea25
7 files changed
+254
-2
Documentation/config/log.adoc
+1
-2
@@ -53,8 +53,7 @@ This is the same as the `--decorate` option of the `git log`.
53
`log.follow`::
54
If `true`, `git log` will act as if the `--follow` option was used when
55
a single <path> is given. This has the same limitations as `--follow`,
56
- i.e. it cannot be used to follow multiple files and does not work well
57
- on non-linear history.
56
+ i.e. it cannot be used to follow multiple files.
57
58
`log.graphColors`::
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A list of colors, separated by commas, that can be used to draw
log-tree.c
+116
@@ -3,6 +3,7 @@
3
4
#include "git-compat-util.h"
5
#include "commit-reach.h"
6
+#include "commit-slab.h"
7
#include "config.h"
8
#include "diff.h"
9
#include "diffcore.h"
@@ -1089,6 +1090,96 @@ static int do_remerge_diff(struct rev_info *opt,
1090
return !opt->loginfo;
1091
}
1092
1093
+/* Per-commit path storage for --follow across merges */
1094
+define_commit_slab(follow_pathspec_slab, char *);
1095
+
1096
+static const char *pathspec_single_path(const struct pathspec *ps)
1097
+{
1098
+ if (ps->nr != 1)
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+ return NULL;
1100
+ return ps->items[0].match;
1101
+}
1102
+
1103
+static void set_pathspec_to_single_path(struct pathspec *ps, const char *path)
1104
+{
1105
+ const char *paths[2] = { path, NULL };
1106
+
1107
+ clear_pathspec(ps);
1108
+ parse_pathspec(ps,
1109
+ PATHSPEC_ALL_MAGIC & ~PATHSPEC_LITERAL,
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+ PATHSPEC_LITERAL_PATH, "", paths);
1111
+}
1112
+
1113
+static void remember_follow_pathspec(struct rev_info *opt,
1114
+ struct commit *c, const char *path)
1115
+{
1116
+ char **slot;
1117
+
1118
+ if (!path)
1119
+ return;
1120
+ if (!opt->follow_pathspec_slab) {
1121
+ opt->follow_pathspec_slab = xmalloc(sizeof(*opt->follow_pathspec_slab));
1122
+ init_follow_pathspec_slab(opt->follow_pathspec_slab);
1123
+ }
1124
+ slot = follow_pathspec_slab_at(opt->follow_pathspec_slab, c);
1125
+ if (*slot && !strcmp(*slot, path))
1126
+ return;
1127
+ free(*slot);
1128
+ *slot = xstrdup(path);
1129
+}
1130
+
1131
+static const char *recall_follow_pathspec(struct rev_info *opt,
1132
+ struct commit *c)
1133
+{
1134
+ char **slot;
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+
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+ if (!opt->follow_pathspec_slab)
1137
+ return NULL;
1138
+ slot = follow_pathspec_slab_peek(opt->follow_pathspec_slab, c);
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+ return slot ? *slot : NULL;
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+}
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+
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+static void free_follow_pathspec_slot(char **slot)
1143
+{
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+ FREE_AND_NULL(*slot);
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+}
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+
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+void release_follow_pathspec_slab(struct rev_info *opt)
1148
+{
1149
+ if (!opt->follow_pathspec_slab)
1150
+ return;
1151
+ deep_clear_follow_pathspec_slab(opt->follow_pathspec_slab,
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+ free_follow_pathspec_slot);
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+ FREE_AND_NULL(opt->follow_pathspec_slab);
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+}
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+
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+/* Compute a path to follow in parent, if there is one */
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+static void propagate_follow_pathspec_to_parent(struct rev_info *opt,
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+ struct commit *commit,
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+ struct commit *parent)
1160
+{
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+ struct diff_options diff_opts;
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+ const char *path;
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+
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+ parse_commit_or_die(parent);
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+ repo_diff_setup(opt->diffopt.repo, &diff_opts);
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+ copy_pathspec(&diff_opts.pathspec, &opt->diffopt.pathspec);
1167
+ diff_opts.flags.recursive = 1;
1168
+ diff_opts.flags.follow_renames = 1;
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+ diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
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+ diff_setup_done(&diff_opts);
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+ diff_tree_oid(get_commit_tree_oid(parent),
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+ get_commit_tree_oid(commit),
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+ "", &diff_opts);
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+
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+ path = pathspec_single_path(&diff_opts.pathspec);
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+ if (path)
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+ remember_follow_pathspec(opt, parent, path);
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+
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+ diff_queue_clear(&diff_queued_diff);
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+ diff_free(&diff_opts);
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+}
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+
1183
/*
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* Show the diff of a commit.
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*
@@ -1185,6 +1276,16 @@ int log_tree_commit(struct rev_info *opt, struct commit *commit)
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opt->loginfo = &log;
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opt->diffopt.no_free = 1;
1278
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+ /* Any recorded path for this commit? If so, restore it */
1280
+ if (opt->diffopt.flags.follow_renames) {
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+ const char *stored = recall_follow_pathspec(opt, commit);
1282
+ if (stored) {
1283
+ const char *current = pathspec_single_path(&opt->diffopt.pathspec);
1284
+ if (!current || strcmp(current, stored))
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+ set_pathspec_to_single_path(&opt->diffopt.pathspec, stored);
1286
+ }
1287
+ }
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+
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if (opt->track_linear && !opt->linear && !opt->reverse_output_stage)
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fprintf(opt->diffopt.file, "\n%s\n", opt->break_bar);
1291
shown = log_tree_diff(opt, commit, &log);
@@ -1197,6 +1298,21 @@ int log_tree_commit(struct rev_info *opt, struct commit *commit)
1298
fprintf(opt->diffopt.file, "\n%s\n", opt->break_bar);
1299
if (shown)
1300
show_diff_of_diff(opt);
1301
+
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+ /* Record what path each parent of this commit should use */
1303
+ if (opt->diffopt.flags.follow_renames) {
1304
+ struct commit_list *parents = get_saved_parents(opt, commit);
1305
+ if (parents && parents->next) {
1306
+ struct commit_list *p;
1307
+ for (p = parents; p; p = p->next)
1308
+ propagate_follow_pathspec_to_parent(opt, commit,
1309
+ p->item);
1310
+ } else if (parents) {
1311
+ remember_follow_pathspec(opt, parents->item,
1312
+ pathspec_single_path(&opt->diffopt.pathspec));
1313
+ }
1314
+ }
1315
+
1316
opt->loginfo = NULL;
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maybe_flush_or_die(opt->diffopt.file, "stdout");
1318
opt->diffopt.no_free = no_free;
log-tree.h
+1
@@ -26,6 +26,7 @@ struct decoration_options {
26
int parse_decorate_color_config(const char *var, const char *slot_name, const char *value);
27
int log_tree_diff_flush(struct rev_info *);
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int log_tree_commit(struct rev_info *, struct commit *);
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+void release_follow_pathspec_slab(struct rev_info *);
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void show_log(struct rev_info *opt);
31
void format_decorations(struct strbuf *sb, const struct commit *commit,
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enum git_colorbool use_color, const struct decoration_options *opts);
revision.c
+2
@@ -26,6 +26,7 @@
26
#include "decorate.h"
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#include "string-list.h"
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#include "line-log.h"
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+#include "log-tree.h"
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#include "mailmap.h"
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#include "commit-slab.h"
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#include "cache-tree.h"
@@ -3304,6 +3305,7 @@ void release_revisions(struct rev_info *revs)
3305
line_log_free(revs);
3306
oidset_clear(&revs->missing_commits);
3307
release_revisions_bloom_keyvecs(revs);
3308
+ release_follow_pathspec_slab(revs);
3309
}
3310
3311
static void add_child(struct rev_info *revs, struct commit *parent, struct commit *child)
revision.h
+4
@@ -66,6 +66,7 @@ struct repository;
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struct rev_info;
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struct string_list;
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struct saved_parents;
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+struct follow_pathspec_slab;
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struct bloom_keyvec;
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struct bloom_filter_settings;
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struct option;
@@ -363,6 +364,9 @@ struct rev_info {
364
/* copies of the parent lists, for --full-diff display */
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struct saved_parents *saved_parents_slab;
366
367
+ /* per-commit pathspec for --follow across merges */
368
+ struct follow_pathspec_slab *follow_pathspec_slab;
369
+
370
struct commit_list *previous_parents;
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struct commit_list *ancestry_path_bottoms;
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const char *break_bar;
t/meson.build
+1
@@ -576,6 +576,7 @@ integration_tests = [
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't4215-log-skewed-merges.sh',
577
't4216-log-bloom.sh',
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't4217-log-limit.sh',
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+ 't4219-log-follow-merge.sh',
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't4252-am-options.sh',
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't4253-am-keep-cr-dos.sh',
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't4254-am-corrupt.sh',
t/t4219-log-follow-merge.sh
new
+129
@@ -0,0 +1,129 @@
1
+#!/bin/sh
2
+
3
+test_description='Test --follow follows renames across merges'
4
+
5
+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=master
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+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
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+
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+. ./test-lib.sh
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+
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+test_expect_success 'setup subtree-merged repository' '
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+ git init inner &&
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+ echo inner >inner/inner.txt &&
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+ git -C inner add inner.txt &&
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+ git -C inner commit -m "inner init" &&
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+
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+ git init outer &&
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+ echo outer >outer/outer.txt &&
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+ git -C outer add outer.txt &&
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+ git -C outer commit -m "outer init" &&
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+
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+ git -C outer fetch ../inner master &&
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+ git -C outer merge -s ours --no-commit --allow-unrelated-histories \
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+ FETCH_HEAD &&
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+ git -C outer read-tree --prefix=inner/ -u FETCH_HEAD &&
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+ git -C outer commit -m "Merge inner repo into inner/ subdirectory"
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+'
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+
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+test_expect_success '--follow finds the pre-merge commit through a subtree merge' '
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+ git -C outer log --follow --pretty=tformat:%s inner/inner.txt >actual &&
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+ echo "inner init" >expect &&
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+ test_cmp expect actual
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+'
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+
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+test_expect_success 'setup merge of two branches that both renamed a file to README' '
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+ git init foo &&
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+ mkdir foo/foo &&
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+ echo "foo readme" >foo/foo/README &&
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+ git -C foo add foo/README &&
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+ git -C foo commit -m "add foo README" &&
40
+
41
+ git -C foo mv foo/README README &&
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+ git -C foo commit -m "promote foo README to toplevel" &&
43
+
44
+ echo "foo c" >foo/foo.c &&
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+ git -C foo add foo.c &&
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+ git -C foo commit -m "add foo C impl" &&
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+
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+ git init bar &&
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+ mkdir bar/bar &&
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+ echo "bar readme" >bar/bar/README &&
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+ git -C bar add bar/README &&
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+ git -C bar commit -m "add bar README" &&
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+
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+ git -C bar mv bar/README README &&
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+ git -C bar commit -m "promote bar README to toplevel" &&
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+
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+ echo "bar c" >bar/bar.c &&
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+ git -C bar add bar.c &&
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+ git -C bar commit -m "add bar C impl" &&
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+
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+ git -C foo fetch ../bar master &&
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+ git -C foo merge -s ours --no-commit --allow-unrelated-histories \
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+ FETCH_HEAD &&
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+ git -C foo checkout FETCH_HEAD -- bar.c &&
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+ git -C foo commit -m "merge bar into foo"
66
+'
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+
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+test_expect_success '--follow follows renames across both sides of a merge' '
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+ git -C foo log --follow --pretty=tformat:%s README >actual &&
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+ sort actual >actual.sorted &&
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+ cat >expect <<-\EOF &&
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+ add bar README
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+ add foo README
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+ promote bar README to toplevel
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+ promote foo README to toplevel
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+ EOF
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+ test_cmp expect actual.sorted
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+'
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+
80
+test_expect_success 'setup diamond with renames on both sides of a fork' '
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+ git init diamond &&
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+ test_lines="line 1\nline 2\nline 3\nline 4\nline 5\n" &&
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+
84
+ printf "$test_lines" >diamond/path0 &&
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+ git -C diamond add path0 &&
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+ git -C diamond commit -m "A: add path0" &&
87
+
88
+ git -C diamond checkout -b upper &&
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+ printf "line 1\nline 2\nline 3 modified by B\nline 4\nline 5\n" \
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+ >diamond/path0 &&
91
+ git -C diamond commit -am "B: modify path0 on upper" &&
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+ git -C diamond mv path0 path1 &&
93
+ git -C diamond commit -m "X: rename path0 to path1" &&
94
+
95
+ git -C diamond checkout -b lower master &&
96
+ printf "line 1\nline 2\nline 3 modified by C\nline 4\nline 5\n" \
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+ >diamond/path0 &&
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+ git -C diamond commit -am "C: modify path0 on lower" &&
99
+ git -C diamond mv path0 path2 &&
100
+ git -C diamond commit -m "Y: rename path0 to path2" &&
101
+
102
+ git -C diamond checkout upper &&
103
+ git -C diamond merge -s ours --no-commit lower &&
104
+ git -C diamond rm path1 &&
105
+ printf "line 1\nline 2\nline 3 merged\nline 4\nline 5\n" \
106
+ >diamond/path &&
107
+ git -C diamond add path &&
108
+ git -C diamond commit -m "M: merge with rename to path" &&
109
+
110
+ printf "line 1\nline 2\nline 3 merged again\nline 4\nline 5\n" \
111
+ >diamond/path &&
112
+ git -C diamond commit -am "Z: modify path"
113
+'
114
+
115
+test_expect_success '--follow follows renames through a fork in a single history' '
116
+ git -C diamond log --follow --pretty=tformat:%s path >actual &&
117
+ sort actual >actual.sorted &&
118
+ cat >expect <<-\EOF &&
119
+ A: add path0
120
+ B: modify path0 on upper
121
+ C: modify path0 on lower
122
+ X: rename path0 to path1
123
+ Y: rename path0 to path2
124
+ Z: modify path
125
+ EOF
126
+ test_cmp expect actual.sorted
127
+'
128
+
129
+test_done