From: Stefan Sperling <stsp@stsp.name>
Subject: Re: show original content in merge conflicts
To: Sebastien Marie <semarie@online.fr>, gameoftrees@openbsd.org
Date: Sat, 19 Oct 2019 15:04:53 +0200

On Fri, Oct 11, 2019 at 12:29:04PM +0200, Stefan Sperling wrote:
> On Fri, Oct 11, 2019 at 11:12:09AM +0200, Sebastien Marie wrote:
> > Do you think it would be valuable to expand it more than just the commit id,
> > with terms like "workdir", "base" or "commit" ? or does it would just add
> > confusion for others people or eventually some tools ?
> > 
> >   <<<<<<< commit 1234....
> >   content of new file in repository
> >   ||||||| base 1235....
> >   content of original file in repository
> >   ======= workdir
> >   content of locally modified file
> >   >>>>>>>
> 
> Yes, I agree that improving the labels like this would be nice.
> I will try to work on that soon.

Coming back to this suggestion from you, how is this?

<<<<<<< merged change: commit 1234abc....
content of new file in repository
||||||| 3-way merge base: commit 5678def....
content of original file in repository
=======
content of locally modified file
>>>>>>>

I think the most important information to display is the commit IDs and
what they represent in terms of input into the merge algorithm.

I have left the ======= and >>>>>>> without further context annotation.
The user already knows the path or directory of the affected file
since they are editing it or are reading a diff of it, so I don't
see the point of showing the filename here.

Does this diff look good?

diff refs/heads/master refs/heads/labels
blob - d8e2403ac8b60843492a2228a507dad1ac532791
blob + 4e9889d1ca69a14aedc6dcae7c29125180dae6cc
--- lib/diff3.c
+++ lib/diff3.c
@@ -146,7 +146,9 @@ struct diff3_state {
 	 * is stored in last[1-3];
 	 */
 	int last[4];
-	char f1mark[PATH_MAX], f3mark[PATH_MAX]; /* markers for -E and -X */
+	char f1mark[PATH_MAX];
+	char f2mark[PATH_MAX];
+	char f3mark[PATH_MAX];
 
 	char *buf;
 
@@ -173,7 +175,7 @@ static const struct got_error *repos(int, struct diff3
 static const struct got_error *increase(struct diff3_state *);
 static const struct got_error *diff3_internal(char *, char *, char *,
     char *, char *, const char *, const char *, struct diff3_state *,
-    const char *, const char *);
+    const char *, const char *, const char *);
 
 static const struct got_error *
 diff_output(BUF *diffbuf, const char *fmt, ...)
@@ -269,7 +271,7 @@ done:
  */
 const struct got_error *
 got_merge_diff3(int *overlapcnt, int outfd, const char *p1, const char *p2,
-    const char *p3, const char *label1, const char *label3)
+    const char *p3, const char *label1, const char *label2, const char *label3)
 {
 	const struct got_error *err = NULL;
 	char *dp13, *dp23, *path1, *path2, *path3;
@@ -367,7 +369,7 @@ got_merge_diff3(int *overlapcnt, int outfd, const char
 
 	d3s->diffbuf = diffb;
 	err = diff3_internal(dp13, dp23, path1, path2, path3,
-	    label1, label3, d3s, label1, label3);
+	    label1, label3, d3s, label1, label2, label3);
 	if (err) {
 		buf_free(diffb);
 		diffb = NULL;
@@ -422,19 +424,27 @@ out:
 static const struct got_error *
 diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
     const char *fmark, const char *rmark, struct diff3_state *d3s,
-    const char *label1, const char *label3)
+    const char *label1, const char *label2, const char *label3)
 {
 	const struct got_error *err = NULL;
 	ssize_t m, n;
 	int i;
 
 	i = snprintf(d3s->f1mark, sizeof(d3s->f1mark),
-	    "%s %s", GOT_DIFF_CONFLICT_MARKER_BEGIN, label1);
+	    "%s%s%s", GOT_DIFF_CONFLICT_MARKER_BEGIN,
+	    label1 ? " " : "", label1 ? label1 : "");
 	if (i < 0 || i >= (int)sizeof(d3s->f1mark))
 		return got_error(GOT_ERR_NO_SPACE);
 
+	i = snprintf(d3s->f2mark, sizeof(d3s->f2mark),
+	    "%s%s%s", GOT_DIFF_CONFLICT_MARKER_ORIG,
+	    label2 ? " " : "", label2 ? label2 : "");
+	if (i < 0 || i >= (int)sizeof(d3s->f2mark))
+		return got_error(GOT_ERR_NO_SPACE);
+
 	i = snprintf(d3s->f3mark, sizeof(d3s->f3mark),
-	    "%s %s", GOT_DIFF_CONFLICT_MARKER_END, label3);
+	    "%s%s%s", GOT_DIFF_CONFLICT_MARKER_END,
+	    label3 ? " " : "", label3 ? label3 : "");
 	if (i < 0 || i >= (int)sizeof(d3s->f3mark))
 		return got_error(GOT_ERR_NO_SPACE);
 
@@ -983,8 +993,7 @@ edscript(int n, struct diff3_state *d3s)
 		} else if (d3s->de[n].oldo.from < d3s->de[n].oldo.to) {
 			/* Output a block of 3-way diff base file content. */
 			err = diff_output(d3s->diffbuf, "%da\n%s\n",
-			    d3s->de[n].old.to -1,
-			    GOT_DIFF_CONFLICT_MARKER_ORIG);
+			    d3s->de[n].old.to - 1, d3s->f2mark);
 			if (err)
 				return err;
 			if (fseeko(d3s->fp[1], d3s->de[n].oldo.from, SEEK_SET)
blob - 0d74b1bbdb78b195fcfd6b16c5042af2a781aa5f
blob + ace2137e04157dfffb2d383748e8d9561c074ac1
--- lib/got_lib_diff.h
+++ lib/got_lib_diff.h
@@ -150,7 +150,7 @@ const struct got_error *got_diff_blob_file_lines_chang
 void got_diff_free_changes(struct got_diff_changes *);
 
 const struct got_error *got_merge_diff3(int *, int, const char *, const char *,
-    const char *, const char *, const char *);
+    const char *, const char *, const char *, const char *);
 
 const struct got_error *got_diff_files(struct got_diff_changes **,
     struct got_diff_state **, struct got_diff_args **, int *, FILE *, size_t,
blob - e289542324a5a24dba52bcccb0d657378875d631
blob + c4df32a19603acd84d6a098d33892f92581f2f71
--- lib/worktree.c
+++ lib/worktree.c
@@ -60,6 +60,9 @@
 #define	MIN(_a,_b) ((_a) < (_b) ? (_a) : (_b))
 #endif
 
+#define GOT_MERGE_LABEL_MERGED	"merged change"
+#define GOT_MERGE_LABEL_BASE	"3-way merge base"
+
 static const struct got_error *
 create_meta_file(const char *path_got, const char *name, const char *content)
 {
@@ -728,7 +731,8 @@ static const struct got_error *
 merge_file(int *local_changes_subsumed, struct got_worktree *worktree,
     struct got_blob_object *blob_orig, const char *ondisk_path,
     const char *path, uint16_t st_mode, const char *deriv_path,
-    const char *label_deriv, struct got_repository *repo,
+    const char *label_orig, const char *label_deriv,
+    struct got_repository *repo,
     got_worktree_checkout_cb progress_cb, void *progress_arg)
 {
 	const struct got_error *err = NULL;
@@ -776,7 +780,7 @@ merge_file(int *local_changes_subsumed, struct got_wor
 	}
 
 	err = got_merge_diff3(&overlapcnt, merged_fd, deriv_path,
-	    blob_orig_path, ondisk_path, label_deriv, path);
+	    blob_orig_path, ondisk_path, label_deriv, label_orig, NULL);
 	if (err)
 		goto done;
 
@@ -832,10 +836,10 @@ done:
 static const struct got_error *
 merge_blob(int *local_changes_subsumed, struct got_worktree *worktree,
     struct got_blob_object *blob_orig, const char *ondisk_path,
-    const char *path, uint16_t st_mode, struct got_blob_object *blob_deriv,
-    struct got_object_id *deriv_base_commit_id,
-    struct got_repository *repo, got_worktree_checkout_cb progress_cb,
-    void *progress_arg)
+    const char *path, uint16_t st_mode, const char *label_orig,
+    struct got_blob_object *blob_deriv,
+    struct got_object_id *deriv_base_commit_id, struct got_repository *repo,
+    got_worktree_checkout_cb progress_cb, void *progress_arg)
 {
 	const struct got_error *err = NULL;
 	FILE *f_deriv = NULL;
@@ -866,14 +870,15 @@ merge_blob(int *local_changes_subsumed, struct got_wor
 	err = got_object_id_str(&id_str, deriv_base_commit_id);
 	if (err)
 		goto done;
-	if (asprintf(&label_deriv, "commit %s", id_str) == -1) {
+	if (asprintf(&label_deriv, "%s: commit %s",
+	    GOT_MERGE_LABEL_MERGED, id_str) == -1) {
 		err = got_error_from_errno("asprintf");
 		goto done;
 	}
 
 	err = merge_file(local_changes_subsumed, worktree, blob_orig,
-	    ondisk_path, path, st_mode, blob_deriv_path, label_deriv,
-	    repo, progress_cb, progress_arg);
+	    ondisk_path, path, st_mode, blob_deriv_path, label_orig,
+	    label_deriv, repo, progress_cb, progress_arg);
 done:
 	if (f_deriv && fclose(f_deriv) != 0 && err == NULL)
 		err = got_error_from_errno("fclose");
@@ -1280,6 +1285,7 @@ update_blob(struct got_worktree *worktree,
 	if (status == GOT_STATUS_MODIFY || status == GOT_STATUS_ADD) {
 		int update_timestamps;
 		struct got_blob_object *blob2 = NULL;
+		char *label_orig = NULL;
 		if (got_fileindex_entry_has_blob(ie)) {
 			struct got_object_id id2;
 			memcpy(id2.sha1, ie->blob_sha1, SHA1_DIGEST_LENGTH);
@@ -1287,10 +1293,24 @@ update_blob(struct got_worktree *worktree,
 			if (err)
 				goto done;
 		}
+		if (got_fileindex_entry_has_commit(ie)) {
+			char id_str[SHA1_DIGEST_STRING_LENGTH];
+			if (got_sha1_digest_to_str(ie->commit_sha1, id_str,
+			    sizeof(id_str)) == NULL) {
+				err = got_error(GOT_ERR_BAD_OBJ_ID_STR);
+				goto done;
+			}
+			if (asprintf(&label_orig, "%s: commit %s",
+			    GOT_MERGE_LABEL_BASE, id_str) == -1) {
+				err = got_error_from_errno("asprintf");
+				goto done;
+			}
+		}
 		err = merge_blob(&update_timestamps, worktree, blob2,
-		    ondisk_path, path, sb.st_mode, blob,
+		    ondisk_path, path, sb.st_mode, label_orig, blob,
 		    worktree->base_commit_id, repo,
 		    progress_cb, progress_arg);
+		free(label_orig);
 		if (blob2)
 			got_object_blob_close(blob2);
 		if (err)
@@ -1979,6 +1999,7 @@ struct merge_file_cb_arg {
     void *progress_arg;
     got_cancel_cb cancel_cb;
     void *cancel_arg;
+    const char *label_orig;
     struct got_object_id *commit_id2;
 };
 
@@ -2025,8 +2046,8 @@ merge_file_cb(void *arg, struct got_blob_object *blob1
 		}
 
 		err = merge_blob(&local_changes_subsumed, a->worktree, blob1,
-		    ondisk_path, path2, sb.st_mode, blob2, a->commit_id2, repo,
-		    a->progress_cb, a->progress_arg);
+		    ondisk_path, path2, sb.st_mode, a->label_orig, blob2,
+		    a->commit_id2, repo, a->progress_cb, a->progress_arg);
 	} else if (blob1) {
 		ie = got_fileindex_entry_get(a->fileindex, path1,
 		    strlen(path1));
@@ -2099,9 +2120,10 @@ merge_file_cb(void *arg, struct got_blob_object *blob1
 				goto done;
 			}
 			err = merge_blob(&local_changes_subsumed, a->worktree,
-			    NULL, ondisk_path, path2, sb.st_mode, blob2,
-			    a->commit_id2, repo,
-			    a->progress_cb, a->progress_arg);
+			    NULL, ondisk_path, path2, sb.st_mode,
+			    a->label_orig, blob2, a->commit_id2, repo,
+			    a->progress_cb,
+			    a->progress_arg);
 			if (status == GOT_STATUS_DELETE) {
 				err = update_blob_fileindex_entry(a->worktree,
 				    a->fileindex, ie, ondisk_path, ie->path,
@@ -2178,8 +2200,11 @@ merge_files(struct got_worktree *worktree, struct got_
 	struct got_object_id *tree_id1 = NULL, *tree_id2 = NULL;
 	struct got_tree_object *tree1 = NULL, *tree2 = NULL;
 	struct merge_file_cb_arg arg;
+	char *label_orig = NULL;
 
 	if (commit_id1) {
+		char *id_str;
+
 		err = got_object_id_by_path(&tree_id1, repo, commit_id1,
 		    worktree->path_prefix);
 		if (err)
@@ -2188,6 +2213,18 @@ merge_files(struct got_worktree *worktree, struct got_
 		err = got_object_open_as_tree(&tree1, repo, tree_id1);
 		if (err)
 			goto done;
+
+		err = got_object_id_str(&id_str, commit_id1);
+		if (err)
+			goto done;
+
+		if (asprintf(&label_orig, "%s: commit %s",
+		    GOT_MERGE_LABEL_BASE, id_str) == -1) {
+			err = got_error_from_errno("asprintf");
+			free(id_str);
+			goto done;
+		}
+		free(id_str);
 	}
 
 	err = got_object_id_by_path(&tree_id2, repo, commit_id2,
@@ -2205,6 +2242,7 @@ merge_files(struct got_worktree *worktree, struct got_
 	arg.progress_arg = progress_arg;
 	arg.cancel_cb = cancel_cb;
 	arg.cancel_arg = cancel_arg;
+	arg.label_orig = label_orig;
 	arg.commit_id2 = commit_id2;
 	err = got_diff_tree(tree1, tree2, "", "", repo, merge_file_cb, &arg, 1);
 	sync_err = sync_fileindex(fileindex, fileindex_path);
@@ -2215,6 +2253,7 @@ done:
 		got_object_tree_close(tree1);
 	if (tree2)
 		got_object_tree_close(tree2);
+	free(label_orig);
 	return err;
 }
 
@@ -6227,6 +6266,7 @@ unstage_path(void *arg, unsigned char status,
 	struct got_blob_object *blob_base = NULL, *blob_staged = NULL;
 	char *ondisk_path = NULL, *path_unstaged_content = NULL;
 	char *path_new_staged_content = NULL;
+	char *id_str = NULL, *label_orig = NULL;
 	int local_changes_subsumed;
 	struct stat sb;
 
@@ -6243,6 +6283,16 @@ unstage_path(void *arg, unsigned char status,
 	    == -1)
 		return got_error_from_errno("asprintf");
 
+	err = got_object_id_str(&id_str,
+	    commit_id ? commit_id : a->worktree->base_commit_id);
+	if (err)
+		goto done;
+	if (asprintf(&label_orig, "%s: commit %s", GOT_MERGE_LABEL_BASE,
+	    id_str) == -1) {
+		err = got_error_from_errno("asprintf");
+		goto done;
+	}
+
 	switch (staged_status) {
 	case GOT_STATUS_MODIFY:
 		err = got_object_open_as_blob(&blob_base, a->repo,
@@ -6282,8 +6332,9 @@ unstage_path(void *arg, unsigned char status,
 				err = merge_file(&local_changes_subsumed,
 				    a->worktree, blob_base, ondisk_path,
 				    relpath, got_fileindex_perms_to_st(ie),
-				    path_unstaged_content, "unstaged",
-				    a->repo, a->progress_cb, a->progress_arg);
+				    path_unstaged_content, label_orig,
+				    "unstaged", a->repo, a->progress_cb,
+				    a->progress_arg);
 				if (err == NULL &&
 				    path_new_staged_content == NULL)
 					got_fileindex_entry_stage_set(ie,
@@ -6297,7 +6348,7 @@ unstage_path(void *arg, unsigned char status,
 			break;
 		err = merge_blob(&local_changes_subsumed, a->worktree,
 		    blob_base, ondisk_path, relpath,
-		    got_fileindex_perms_to_st(ie), blob_staged,
+		    got_fileindex_perms_to_st(ie), label_orig, blob_staged,
 		    commit_id ? commit_id : a->worktree->base_commit_id,
 		    a->repo, a->progress_cb, a->progress_arg);
 		if (err == NULL)
@@ -6325,7 +6376,7 @@ unstage_path(void *arg, unsigned char status,
 		err = (*a->progress_cb)(a->progress_arg, status, relpath);
 		break;
 	}
-
+done:
 	free(ondisk_path);
 	if (path_unstaged_content &&
 	    unlink(path_unstaged_content) == -1 && err == NULL)
@@ -6339,6 +6390,8 @@ unstage_path(void *arg, unsigned char status,
 		got_object_blob_close(blob_base);
 	if (blob_staged)
 		got_object_blob_close(blob_staged);
+	free(id_str);
+	free(label_orig);
 	return err;
 }
 
blob - 31587c10a62466ca183a27d0985a8816a43d7053
blob + 43a0f3a840e30d3749f4690d900e34f9cc447465
--- regress/cmdline/diff.sh
+++ regress/cmdline/diff.sh
@@ -102,6 +102,7 @@ function test_diff_shows_conflict {
 	echo "8" >> $testroot/repo/numbers
 	(cd $testroot/repo && git add numbers)
 	git_commit $testroot/repo -m "added numbers file"
+	local base_commit=`git_show_head $testroot/repo`
 
 	got checkout $testroot/repo $testroot/wt > /dev/null
 	ret="$?"
@@ -142,25 +143,29 @@ function test_diff_shows_conflict {
 	echo '+++ numbers' >> $testroot/stdout.expected
 	echo '@@ -1,8 +1,20 @@' >> $testroot/stdout.expected
 	echo ' 1' >> $testroot/stdout.expected
-	echo "+<<<<<<< commit $head_rev" >> $testroot/stdout.expected
+	echo "+<<<<<<< merged change: commit $head_rev" \
+		>> $testroot/stdout.expected
 	echo ' 22' >> $testroot/stdout.expected
-	echo '+|||||||' >> $testroot/stdout.expected
+	echo "+||||||| 3-way merge base: commit $base_commit" \
+		>> $testroot/stdout.expected
 	echo '+2' >> $testroot/stdout.expected
 	echo '+=======' >> $testroot/stdout.expected
 	echo '+77' >> $testroot/stdout.expected
-	echo '+>>>>>>> numbers' >> $testroot/stdout.expected
+	echo '+>>>>>>>' >> $testroot/stdout.expected
 	echo ' 3' >> $testroot/stdout.expected
 	echo ' 4' >> $testroot/stdout.expected
 	echo ' 5' >> $testroot/stdout.expected
 	echo ' 6' >> $testroot/stdout.expected
 	echo ' 7' >> $testroot/stdout.expected
-	echo "+<<<<<<< commit $head_rev" >> $testroot/stdout.expected
+	echo "+<<<<<<< merged change: commit $head_rev" \
+		>> $testroot/stdout.expected
 	echo ' 33' >> $testroot/stdout.expected
-	echo '+|||||||' >> $testroot/stdout.expected
+	echo "+||||||| 3-way merge base: commit $base_commit" \
+		>> $testroot/stdout.expected
 	echo '+8' >> $testroot/stdout.expected
 	echo '+=======' >> $testroot/stdout.expected
 	echo '+88' >> $testroot/stdout.expected
-	echo '+>>>>>>> numbers' >> $testroot/stdout.expected
+	echo '+>>>>>>>' >> $testroot/stdout.expected
 
 	(cd $testroot/wt && got diff > $testroot/stdout)
 
blob - c94727a0b05067fb3a4deadd1017588265245e68
blob + 62a0455a66d4559f543efeddcfbe821bfa742d26
--- regress/cmdline/rebase.sh
+++ regress/cmdline/rebase.sh
@@ -176,6 +176,7 @@ function test_rebase_ancestry_check {
 
 function test_rebase_continue {
 	local testroot=`test_init rebase_continue`
+	local init_commit=`git_show_head $testroot/repo`
 
 	(cd $testroot/repo && git checkout -q -b newbranch)
 	echo "modified alpha on branch" > $testroot/repo/alpha
@@ -216,13 +217,15 @@ function test_rebase_continue {
 		return 1
 	fi
 
-	echo "<<<<<<< commit $orig_commit1" > $testroot/content.expected
+	echo "<<<<<<< merged change: commit $orig_commit1" \
+		> $testroot/content.expected
 	echo "modified alpha on branch" >> $testroot/content.expected
-	echo "|||||||" >> $testroot/content.expected
+	echo "||||||| 3-way merge base: commit $init_commit" \
+		>> $testroot/content.expected
 	echo "alpha" >> $testroot/content.expected
 	echo "=======" >> $testroot/content.expected
 	echo "modified alpha on master" >> $testroot/content.expected
-	echo '>>>>>>> alpha' >> $testroot/content.expected
+	echo '>>>>>>>' >> $testroot/content.expected
 	cat $testroot/wt/alpha > $testroot/content
 	cmp -s $testroot/content.expected $testroot/content
 	ret="$?"
@@ -347,13 +350,15 @@ function test_rebase_abort {
 		return 1
 	fi
 
-	echo "<<<<<<< commit $orig_commit1" > $testroot/content.expected
+	echo "<<<<<<< merged change: commit $orig_commit1" \
+		> $testroot/content.expected
 	echo "modified alpha on branch" >> $testroot/content.expected
-	echo "|||||||" >> $testroot/content.expected
+	echo "||||||| 3-way merge base: commit $init_commit" \
+		>> $testroot/content.expected
 	echo "alpha" >> $testroot/content.expected
 	echo "=======" >> $testroot/content.expected
 	echo "modified alpha on master" >> $testroot/content.expected
-	echo '>>>>>>> alpha' >> $testroot/content.expected
+	echo '>>>>>>>' >> $testroot/content.expected
 	cat $testroot/wt/alpha > $testroot/content
 	cmp -s $testroot/content.expected $testroot/content
 	ret="$?"
@@ -457,13 +462,15 @@ function test_rebase_no_op_change {
 		return 1
 	fi
 
-	echo "<<<<<<< commit $orig_commit1" > $testroot/content.expected
+	echo "<<<<<<< merged change: commit $orig_commit1" \
+		> $testroot/content.expected
 	echo "modified alpha on branch" >> $testroot/content.expected
-	echo "|||||||" >> $testroot/content.expected
+	echo "||||||| 3-way merge base: commit $init_commit" \
+		>> $testroot/content.expected
 	echo "alpha" >> $testroot/content.expected
 	echo "=======" >> $testroot/content.expected
 	echo "modified alpha on master" >> $testroot/content.expected
-	echo '>>>>>>> alpha' >> $testroot/content.expected
+	echo '>>>>>>>' >> $testroot/content.expected
 	cat $testroot/wt/alpha > $testroot/content
 	cmp -s $testroot/content.expected $testroot/content
 	ret="$?"
@@ -564,13 +571,15 @@ function test_rebase_in_progress {
 		return 1
 	fi
 
-	echo "<<<<<<< commit $orig_commit1" > $testroot/content.expected
+	echo "<<<<<<< merged change: commit $orig_commit1" \
+		> $testroot/content.expected
 	echo "modified alpha on branch" >> $testroot/content.expected
-	echo "|||||||" >> $testroot/content.expected
+	echo "||||||| 3-way merge base: commit $init_commit" \
+		>> $testroot/content.expected
 	echo "alpha" >> $testroot/content.expected
 	echo "=======" >> $testroot/content.expected
 	echo "modified alpha on master" >> $testroot/content.expected
-	echo '>>>>>>> alpha' >> $testroot/content.expected
+	echo '>>>>>>>' >> $testroot/content.expected
 	cat $testroot/wt/alpha > $testroot/content
 	cmp -s $testroot/content.expected $testroot/content
 	ret="$?"
blob - 4aa56793bd1b5831b7a8e3680b244722e712a0dd
blob + 2225b5ae82ab9273a4760df29891aa221c5898b3
--- regress/cmdline/update.sh
+++ regress/cmdline/update.sh
@@ -642,6 +642,7 @@ function test_update_merges_file_edits {
 	echo "8" >> $testroot/repo/numbers
 	(cd $testroot/repo && git add numbers)
 	git_commit $testroot/repo -m "added numbers file"
+	local base_commit=`git_show_head $testroot/repo`
 
 	got checkout $testroot/repo $testroot/wt > /dev/null
 	ret="$?"
@@ -676,15 +677,16 @@ function test_update_merges_file_edits {
 		return 1
 	fi
 
-	echo -n "<<<<<<< commit " > $testroot/content.expected
+	echo -n "<<<<<<< merged change: commit " > $testroot/content.expected
 	git_show_head $testroot/repo >> $testroot/content.expected
 	echo >> $testroot/content.expected
 	echo "modified alpha" >> $testroot/content.expected
-	echo "|||||||" >> $testroot/content.expected
+	echo "||||||| 3-way merge base: commit $base_commit" \
+		>> $testroot/content.expected
 	echo "alpha" >> $testroot/content.expected
 	echo "=======" >> $testroot/content.expected
 	echo "modified alpha, too" >> $testroot/content.expected
-	echo '>>>>>>> alpha' >> $testroot/content.expected
+	echo '>>>>>>>' >> $testroot/content.expected
 	echo "modified beta" >> $testroot/content.expected
 	echo "1" >> $testroot/content.expected
 	echo "22" >> $testroot/content.expected
@@ -881,13 +883,13 @@ function test_update_conflict_wt_add_vs_repo_add {
 		return 1
 	fi
 
-	echo -n "<<<<<<< commit " > $testroot/content.expected
+	echo -n "<<<<<<< merged change: commit " > $testroot/content.expected
 	git_show_head $testroot/repo >> $testroot/content.expected
 	echo >> $testroot/content.expected
 	echo "new" >> $testroot/content.expected
 	echo "=======" >> $testroot/content.expected
 	echo "also new" >> $testroot/content.expected
-	echo '>>>>>>> gamma/new' >> $testroot/content.expected
+	echo '>>>>>>>' >> $testroot/content.expected
 
 	cat $testroot/wt/gamma/new > $testroot/content
 
@@ -1323,6 +1325,7 @@ function test_update_moved_branch_ref {
 
 function test_update_to_another_branch {
 	local testroot=`test_init update_to_another_branch`
+	local base_commit=`git_show_head $testroot/repo`
 
 	got checkout $testroot/repo $testroot/wt > /dev/null
 	ret="$?"
@@ -1362,15 +1365,16 @@ function test_update_to_another_branch {
 		return 1
 	fi
 
-	echo -n "<<<<<<< commit " > $testroot/content.expected
+	echo -n "<<<<<<< merged change: commit " > $testroot/content.expected
 	git_show_head $testroot/repo >> $testroot/content.expected
 	echo >> $testroot/content.expected
 	echo "modified alpha on new branch" >> $testroot/content.expected
-	echo "|||||||" >> $testroot/content.expected
+	echo "||||||| 3-way merge base: commit $base_commit" \
+		>> $testroot/content.expected
 	echo "alpha" >> $testroot/content.expected
 	echo "=======" >> $testroot/content.expected
 	echo "modified alpha in work tree" >> $testroot/content.expected
-	echo '>>>>>>> alpha' >> $testroot/content.expected
+	echo '>>>>>>>' >> $testroot/content.expected
 
 	cat $testroot/wt/alpha > $testroot/content