git_backend: write trees involved in conflict in git commit header

We haven't used custom Git commit headers for two main reasons:

1. I don't want commits created by jj to be different from any other
   commits. I don't want Git projects to get annoyed by such commit
   and reject them.

2. I've been concerned that tools don't know how to handle such
   headers, perhaps even resulting in crashes.

The first argument doesn't apply to commits with conflicts because
such commits would never be accepted by a project whether or not they
use custom commit headers. The second argument is less relevant for
conflicted commits because most tools will be confused by such commits
anyway.

Storing conflict information in commit headers means that we can
transfer them via the regular Git wire protocol. We already include
the tree objects nested inside the root-level tree, so they will also
be transferred.

So, let's start by writing the information redundantly to the commit
header and to the existing storage. That way we can roll it back if we
realize there's a problem with using commit headers.

cli/tests/test_chmod_command.rs

@@ -224,13 +224,13 @@ fn test_chmod_file_dir_deletion_conflicts() {
     insta::assert_snapshot!(stdout, @"");
     insta::assert_snapshot!(stderr, @r###"
     New conflicts appeared in these commits:
-      kmkuslsw 4cc432b5 file_deletion | (conflict) file_deletion
+      kmkuslsw b4c38719 file_deletion | (conflict) file_deletion
     To resolve the conflicts, start by updating to it:
       jj new kmkuslswpqwq
     Then use `jj resolve`, or edit the conflict markers in the file directly.
     Once the conflicts are resolved, you may want inspect the result with `jj diff`.
     Then run `jj squash` to move the resolution into the conflicted commit.
-    Working copy now at: kmkuslsw 4cc432b5 file_deletion | (conflict) file_deletion
+    Working copy now at: kmkuslsw b4c38719 file_deletion | (conflict) file_deletion
     Parent commit      : zsuskuln c51c9c55 file | file
     Parent commit      : royxmykx 6b18b3c1 deletion | deletion
     Added 0 files, modified 1 files, removed 0 files

cli/tests/test_diffedit_command.rs

@@ -379,10 +379,10 @@ fn test_diffedit_merge() {
     let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["diffedit", "-r", "@-"]);
     insta::assert_snapshot!(stdout, @"");
     insta::assert_snapshot!(stderr, @r###"
-    Created royxmykx 2b5202ae (conflict) merge
+    Created royxmykx b90654a0 (conflict) merge
     Rebased 1 descendant commits
-    Working copy now at: yqosqzyt 23b1fe1b (conflict) (empty) (no description set)
-    Parent commit      : royxmykx 2b5202ae (conflict) merge
+    Working copy now at: yqosqzyt 1de824f2 (conflict) (empty) (no description set)
+    Parent commit      : royxmykx b90654a0 (conflict) merge
     Added 0 files, modified 0 files, removed 1 files
     "###);
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "-s", "-r", "@-"]);

cli/tests/test_git_push.rs

@@ -577,7 +577,7 @@ fn test_git_push_conflict() {
     test_env.jj_cmd_ok(&workspace_root, &["describe", "-m", "third"]);
     let stderr = test_env.jj_cmd_failure(&workspace_root, &["git", "push", "--all"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Won't push commit 1973d389875c since it has conflicts
+    Error: Won't push commit d9ca3146ade7 since it has conflicts
     "###);
 }
 

cli/tests/test_immutable_commits.rs

@@ -100,7 +100,7 @@ fn test_rewrite_immutable_commands() {
     insta::assert_snapshot!(stdout, @r###"
     @  yqosqzyt [email protected] 2001-02-03 04:05:13.000 +07:00 3f89addf
     │  (empty) (no description set)
-    │ ◉  mzvwutvl [email protected] 2001-02-03 04:05:11.000 +07:00 main 16ca9d80 conflict
+    │ ◉  mzvwutvl [email protected] 2001-02-03 04:05:11.000 +07:00 main 3d14df18 conflict
     ╭─┤  (empty) merge
     │ │
     │ ~
@@ -113,61 +113,61 @@ fn test_rewrite_immutable_commands() {
     // abandon
     let stderr = test_env.jj_cmd_failure(&repo_path, &["abandon", "main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // chmod
     let stderr = test_env.jj_cmd_failure(&repo_path, &["chmod", "-r=main", "x", "file"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // describe
     let stderr = test_env.jj_cmd_failure(&repo_path, &["describe", "main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // diffedit
     let stderr = test_env.jj_cmd_failure(&repo_path, &["diffedit", "-r=main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // edit
     let stderr = test_env.jj_cmd_failure(&repo_path, &["edit", "main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // move --from
     let stderr = test_env.jj_cmd_failure(&repo_path, &["move", "--from=main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // move --to
     let stderr = test_env.jj_cmd_failure(&repo_path, &["move", "--to=main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // new --insert-before
     let stderr = test_env.jj_cmd_failure(&repo_path, &["new", "--insert-before", "main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // new --insert-after parent_of_main
     let stderr = test_env.jj_cmd_failure(&repo_path, &["new", "--insert-after", "description(b)"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // rebase -s
     let stderr = test_env.jj_cmd_failure(&repo_path, &["rebase", "-s=main", "-d=@"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // rebase -b
@@ -179,43 +179,43 @@ fn test_rewrite_immutable_commands() {
     // rebase -r
     let stderr = test_env.jj_cmd_failure(&repo_path, &["rebase", "-r=main", "-d=@"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // resolve
     let stderr = test_env.jj_cmd_failure(&repo_path, &["resolve", "-r=description(merge)", "file"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // restore -c
     let stderr = test_env.jj_cmd_failure(&repo_path, &["restore", "-c=main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // restore --to
     let stderr = test_env.jj_cmd_failure(&repo_path, &["restore", "--to=main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // split
     let stderr = test_env.jj_cmd_failure(&repo_path, &["split", "-r=main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // squash
     let stderr = test_env.jj_cmd_failure(&repo_path, &["squash", "-r=main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // unsquash
     let stderr = test_env.jj_cmd_failure(&repo_path, &["unsquash", "-r=main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 16ca9d800b08 is immutable
+    Error: Commit 3d14df18607e is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
 }

cli/tests/test_obslog_command.rs

@@ -31,7 +31,7 @@ fn test_obslog_with_or_without_diff() {
     insta::assert_snapshot!(stdout, @r###"
     @  rlvkpnrz [email protected] 2001-02-03 04:05:10.000 +07:00 66b42ad3
     │  my description
-    ◉  rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 5f4634a5 conflict
+    ◉  rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 ebc23d4b conflict
     │  my description
     ◉  rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 6fbba7bc
     │  my description
@@ -44,11 +44,11 @@ fn test_obslog_with_or_without_diff() {
     insta::assert_snapshot!(stdout, @r###"
     @  rlvkpnrz [38;5;[email protected] 2001-02-03 04:05:10.000 +07:00 66b42ad3
     │  my description
-    ◉  [1m[39mr[0m[38;5;8mlvkpnrz[39m hidden [38;5;[email protected][39m [38;5;6m2001-02-03 04:05:09.000 +07:00[39m [1m[38;5;4m5[0m[38;5;8mf4634a5[39m [38;5;1mconflict[39m
+    ◉  [1m[39mr[0m[38;5;8mlvkpnrz[39m hidden [38;5;[email protected][39m [38;5;6m2001-02-03 04:05:09.000 +07:00[39m [1m[38;5;4meb[0m[38;5;8mc23d4b[39m [38;5;1mconflict[39m
     │  my description
     ◉  rlvkpnrz hidden [38;5;[email protected] 2001-02-03 04:05:09.000 +07:00 6fbba7bc
     │  my description
-    ◉  [1m[39mr[0m[38;5;8mlvkpnrz[39m hidden [38;5;[email protected][39m [38;5;6m2001-02-03 04:05:08.000 +07:00[39m [1m[38;5;4me[0m[38;5;8mac0d0da[39m
+    ◉  [1m[39mr[0m[38;5;8mlvkpnrz[39m hidden [38;5;[email protected][39m [38;5;6m2001-02-03 04:05:08.000 +07:00[39m [1m[38;5;4mea[0m[38;5;8mc0d0da[39m
        (empty) my description
     "###);
 
@@ -66,7 +66,7 @@ fn test_obslog_with_or_without_diff() {
     │     5     : foo
     │     6     : bar
     │     7     : >>>>>>>
-    ◉  rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 5f4634a5 conflict
+    ◉  rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 ebc23d4b conflict
     │  my description
     ◉  rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 6fbba7bc
     │  my description
@@ -84,7 +84,7 @@ fn test_obslog_with_or_without_diff() {
     insta::assert_snapshot!(stdout, @r###"
     @  rlvkpnrz [email protected] 2001-02-03 04:05:10.000 +07:00 66b42ad3
     │  my description
-    ◉  rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 5f4634a5 conflict
+    ◉  rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 ebc23d4b conflict
     │  my description
     "###);
 
@@ -93,7 +93,7 @@ fn test_obslog_with_or_without_diff() {
     insta::assert_snapshot!(stdout, @r###"
     rlvkpnrz [email protected] 2001-02-03 04:05:10.000 +07:00 66b42ad3
     my description
-    rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 5f4634a5 conflict
+    rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 ebc23d4b conflict
     my description
     rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 6fbba7bc
     my description
@@ -119,7 +119,7 @@ fn test_obslog_with_or_without_diff() {
     -bar
     ->>>>>>>
     +resolved
-    rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 5f4634a5 conflict
+    rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 ebc23d4b conflict
     my description
     rlvkpnrz hidden [email protected] 2001-02-03 04:05:09.000 +07:00 6fbba7bc
     my description

cli/tests/test_repo_change_report.rs

@@ -33,15 +33,15 @@ fn test_report_conflicts() {
     insta::assert_snapshot!(stderr, @r###"
     Rebased 3 commits
     New conflicts appeared in these commits:
-      kkmpptxz a2593769 (conflict) C
-      rlvkpnrz 727244df (conflict) B
+      kkmpptxz 9baab11e (conflict) C
+      rlvkpnrz de73196a (conflict) B
     To resolve the conflicts, start by updating to the first one:
       jj new rlvkpnrzqnoo
     Then use `jj resolve`, or edit the conflict markers in the file directly.
     Once the conflicts are resolved, you may want inspect the result with `jj diff`.
     Then run `jj squash` to move the resolution into the conflicted commit.
-    Working copy now at: zsuskuln 30928080 (conflict) (empty) (no description set)
-    Parent commit      : kkmpptxz a2593769 (conflict) C
+    Working copy now at: zsuskuln 7dc9bf15 (conflict) (empty) (no description set)
+    Parent commit      : kkmpptxz 9baab11e (conflict) C
     Added 0 files, modified 1 files, removed 0 files
     "###);
 
@@ -50,8 +50,8 @@ fn test_report_conflicts() {
     insta::assert_snapshot!(stderr, @r###"
     Rebased 3 commits
     Existing conflicts were resolved or abandoned from these commits:
-      kkmpptxz hidden a2593769 (conflict) C
-      rlvkpnrz hidden 727244df (conflict) B
+      kkmpptxz hidden 9baab11e (conflict) C
+      rlvkpnrz hidden de73196a (conflict) B
     Working copy now at: zsuskuln 355a2e34 (empty) (no description set)
     Parent commit      : kkmpptxz ed071401 C
     Added 0 files, modified 1 files, removed 0 files
@@ -64,33 +64,33 @@ fn test_report_conflicts() {
     insta::assert_snapshot!(stderr, @r###"
     Also rebased 2 descendant commits onto parent of rebased commit
     New conflicts appeared in these commits:
-      rlvkpnrz 9df65f08 (conflict) B
-      kkmpptxz 7530822d (conflict) C
+      rlvkpnrz e93270ab (conflict) B
+      kkmpptxz 4f0eeaa6 (conflict) C
     To resolve the conflicts, start by updating to one of the first ones:
       jj new rlvkpnrzqnoo
       jj new kkmpptxzrspx
     Then use `jj resolve`, or edit the conflict markers in the file directly.
     Once the conflicts are resolved, you may want inspect the result with `jj diff`.
     Then run `jj squash` to move the resolution into the conflicted commit.
-    Working copy now at: zsuskuln 203be58b (conflict) (empty) (no description set)
-    Parent commit      : kkmpptxz 7530822d (conflict) C
+    Working copy now at: zsuskuln 83074dac (conflict) (empty) (no description set)
+    Parent commit      : kkmpptxz 4f0eeaa6 (conflict) C
     Added 0 files, modified 1 files, removed 0 files
     "###);
 
     // Resolve one of the conflicts by (mostly) following the instructions
     let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["new", "rlvkpnrzqnoo"]);
     insta::assert_snapshot!(stdout, @"");
     insta::assert_snapshot!(stderr, @r###"
-    Working copy now at: vruxwmqv 406f84d0 (conflict) (empty) (no description set)
-    Parent commit      : rlvkpnrz 9df65f08 (conflict) B
+    Working copy now at: vruxwmqv 2ec0b4c3 (conflict) (empty) (no description set)
+    Parent commit      : rlvkpnrz e93270ab (conflict) B
     Added 0 files, modified 1 files, removed 0 files
     "###);
     std::fs::write(repo_path.join("file"), "resolved\n").unwrap();
     let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["squash"]);
     insta::assert_snapshot!(stdout, @"");
     insta::assert_snapshot!(stderr, @r###"
     Existing conflicts were resolved or abandoned from these commits:
-      rlvkpnrz hidden 9df65f08 (conflict) B
+      rlvkpnrz hidden e93270ab (conflict) B
     Working copy now at: yostqsxw 8e160bc4 (empty) (no description set)
     Parent commit      : rlvkpnrz c5319490 B
     "###);
@@ -118,16 +118,16 @@ fn test_report_conflicts_with_divergent_commits() {
     Concurrent modification detected, resolving automatically.
     Rebased 3 commits
     New conflicts appeared in these commits:
-      zsuskuln?? 76c40a95 (conflict) C3
-      zsuskuln?? e92329f2 (conflict) C2
-      kkmpptxz aed319ec (conflict) B
+      zsuskuln?? 94be9a4c (conflict) C3
+      zsuskuln?? cdae4322 (conflict) C2
+      kkmpptxz b76d6a88 (conflict) B
     To resolve the conflicts, start by updating to the first one:
       jj new kkmpptxzrspx
     Then use `jj resolve`, or edit the conflict markers in the file directly.
     Once the conflicts are resolved, you may want inspect the result with `jj diff`.
     Then run `jj squash` to move the resolution into the conflicted commit.
-    Working copy now at: zsuskuln?? e92329f2 (conflict) C2
-    Parent commit      : kkmpptxz aed319ec (conflict) B
+    Working copy now at: zsuskuln?? cdae4322 (conflict) C2
+    Parent commit      : kkmpptxz b76d6a88 (conflict) B
     Added 0 files, modified 1 files, removed 0 files
     "###);
 
@@ -136,9 +136,9 @@ fn test_report_conflicts_with_divergent_commits() {
     insta::assert_snapshot!(stderr, @r###"
     Rebased 3 commits
     Existing conflicts were resolved or abandoned from these commits:
-      zsuskuln hidden 76c40a95 (conflict) C3
-      zsuskuln hidden e92329f2 (conflict) C2
-      kkmpptxz hidden aed319ec (conflict) B
+      zsuskuln hidden 94be9a4c (conflict) C3
+      zsuskuln hidden cdae4322 (conflict) C2
+      kkmpptxz hidden b76d6a88 (conflict) B
     Working copy now at: zsuskuln?? 9c33e9a9 C2
     Parent commit      : kkmpptxz 9ce42c2a B
     Added 0 files, modified 1 files, removed 0 files
@@ -151,13 +151,13 @@ fn test_report_conflicts_with_divergent_commits() {
     insta::assert_snapshot!(stderr, @r###"
     Rebased 1 commits
     New conflicts appeared in these commits:
-      zsuskuln?? 0d6cb6b7 (conflict) C2
+      zsuskuln?? 33752e7e (conflict) C2
     To resolve the conflicts, start by updating to it:
       jj new zsuskulnrvyr
     Then use `jj resolve`, or edit the conflict markers in the file directly.
     Once the conflicts are resolved, you may want inspect the result with `jj diff`.
     Then run `jj squash` to move the resolution into the conflicted commit.
-    Working copy now at: zsuskuln?? 0d6cb6b7 (conflict) C2
+    Working copy now at: zsuskuln?? 33752e7e (conflict) C2
     Parent commit      : zzzzzzzz 00000000 (empty) (no description set)
     Added 0 files, modified 1 files, removed 0 files
     "###);
@@ -168,7 +168,7 @@ fn test_report_conflicts_with_divergent_commits() {
     insta::assert_snapshot!(stderr, @r###"
     Rebased 1 commits
     New conflicts appeared in these commits:
-      zsuskuln?? 9652a362 (conflict) C3
+      zsuskuln?? 37bb9c2f (conflict) C3
     To resolve the conflicts, start by updating to it:
       jj new zsuskulnrvyr
     Then use `jj resolve`, or edit the conflict markers in the file directly.
@@ -184,7 +184,7 @@ fn test_report_conflicts_with_divergent_commits() {
     insta::assert_snapshot!(stderr, @r###"
     Rebased 1 commits
     Existing conflicts were resolved or abandoned from these commits:
-      zsuskuln hidden 0d6cb6b7 (conflict) C2
+      zsuskuln hidden 33752e7e (conflict) C2
     Working copy now at: zsuskuln?? 24f79296 C2
     Parent commit      : kkmpptxz 9ce42c2a B
     Added 0 files, modified 1 files, removed 0 files
@@ -198,6 +198,6 @@ fn test_report_conflicts_with_divergent_commits() {
     insta::assert_snapshot!(stderr, @r###"
     Rebased 1 commits
     Existing conflicts were resolved or abandoned from these commits:
-      zsuskuln hidden 9652a362 (conflict) C3
+      zsuskuln hidden 37bb9c2f (conflict) C3
     "###);
 }