git_backend: add a README to conflicted commits

When you use e.g. `git switch` to check out a conflicted commit,
you're going to end up with the `.jjconflicts-*` directories in your
working copy. It's probably not obvious what those mean. This patch
adds a README file to the root tree to try to explain to users what's
going on and how to recover.

The authoritative information about conflicts is stored in the
`jj:trees` commit header. The contents of conflicted commits is only
used for preventing GC. We can therefore add contents to the tree
without much consequence.

cli/tests/test_chmod_command.rs

@@ -120,7 +120,7 @@ fn test_chmod_regular_conflict() {
     let (_stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["chmod", "x", "nonexistent", "file"]);
     insta::assert_snapshot!(stderr, @r###"
     Warning: No matching entries for paths: nonexistent
-    Working copy now at: yostqsxw cbc43289 conflict | (conflict) conflict
+    Working copy now at: yostqsxw e5912d62 conflict | (conflict) conflict
     Parent commit      : royxmykx 427fbd2f x | x
     Parent commit      : zsuskuln 3f83a26d n | n
     Added 0 files, modified 1 files, removed 0 files
@@ -213,13 +213,13 @@ fn test_chmod_file_dir_deletion_conflicts() {
     insta::assert_snapshot!(stdout, @"");
     insta::assert_snapshot!(stderr, @r###"
     New conflicts appeared in these commits:
-      kmkuslsw b4c38719 file_deletion | (conflict) file_deletion
+      kmkuslsw 1b2ef84c 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 b4c38719 file_deletion | (conflict) file_deletion
+    Working copy now at: kmkuslsw 1b2ef84c 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 b90654a0 (conflict) merge
+    Created royxmykx b9539d6e (conflict) merge
     Rebased 1 descendant commits
-    Working copy now at: yqosqzyt 1de824f2 (conflict) (empty) (no description set)
-    Parent commit      : royxmykx b90654a0 (conflict) merge
+    Working copy now at: yqosqzyt 0a24ed24 (conflict) (empty) (no description set)
+    Parent commit      : royxmykx b9539d6e (conflict) merge
     Added 0 files, modified 0 files, removed 1 files
     There are unresolved conflicts at these paths:
     file2    2-sided conflict

cli/tests/test_git_push.rs

@@ -628,7 +628,7 @@ 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 d9ca3146ade7 since it has conflicts
+    Error: Won't push commit 739c4f08a056 since it has conflicts
     "###);
 }
 

cli/tests/test_immutable_commits.rs

@@ -116,7 +116,7 @@ fn test_rewrite_immutable_commands() {
     insta::assert_snapshot!(stdout, @r###"
     @  yqosqzyt [email protected] 2001-02-03 08:05:13 3f89addf
     │  (empty) (no description set)
-    │ ◉  mzvwutvl [email protected] 2001-02-03 08:05:11 main 3d14df18 conflict
+    │ ◉  mzvwutvl [email protected] 2001-02-03 08:05:11 main 406c181c conflict
     ╭─┤  (empty) merge
     │ │
     │ ~
@@ -129,71 +129,71 @@ fn test_rewrite_immutable_commands() {
     // abandon
     let stderr = test_env.jj_cmd_failure(&repo_path, &["abandon", "main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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###"
     Warning: `jj move` is deprecated; use `jj squash` instead, which is equivalent
     Warning: `jj move` will be removed in a future version, and this will be a hard error
-    Error: Commit 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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###"
     Warning: `jj move` is deprecated; use `jj squash` instead, which is equivalent
     Warning: `jj move` will be removed in a future version, and this will be a hard error
-    Error: Commit 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // parallelize
     let stderr = test_env.jj_cmd_failure(&repo_path, &["parallelize", "description(b)", "main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // rebase -b
@@ -205,31 +205,31 @@ 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 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 is immutable
     Hint: Configure the set of immutable commits via `revset-aliases.immutable_heads()`.
     "###);
     // squash
@@ -241,7 +241,7 @@ fn test_rewrite_immutable_commands() {
     // unsquash
     let stderr = test_env.jj_cmd_failure(&repo_path, &["unsquash", "-r=main"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Commit 3d14df18607e is immutable
+    Error: Commit 406c181c04d8 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 08:05:10 66b42ad3
     │  my description
-    ◉  rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 ebc23d4b conflict
+    ◉  rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 cf73917d conflict
     │  my description
     ◉  rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 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 08:05:10 66b42ad3
     │  my description
-    ◉  [1m[39mr[0m[38;5;8mlvkpnrz[39m hidden [38;5;[email protected][39m [38;5;6m2001-02-03 08:05:09[39m [1m[38;5;4meb[0m[38;5;8mc23d4b[39m [38;5;1mconflict[39m
+    ◉  [1m[39mr[0m[38;5;8mlvkpnrz[39m hidden [38;5;[email protected][39m [38;5;6m2001-02-03 08:05:09[39m [1m[38;5;4mc[0m[38;5;8mf73917d[39m [38;5;1mconflict[39m
     │  my description
     ◉  rlvkpnrz hidden [38;5;[email protected] 2001-02-03 08:05:09 6fbba7bc
     │  my description
-    ◉  [1m[39mr[0m[38;5;8mlvkpnrz[39m hidden [38;5;[email protected][39m [38;5;6m2001-02-03 08:05:08[39m [1m[38;5;4mea[0m[38;5;8mc0d0da[39m
+    ◉  [1m[39mr[0m[38;5;8mlvkpnrz[39m hidden [38;5;[email protected][39m [38;5;6m2001-02-03 08:05:08[39m [1m[38;5;4me[0m[38;5;8mac0d0da[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 08:05:09 ebc23d4b conflict
+    ◉  rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 cf73917d conflict
     │  my description
     ◉  rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 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 08:05:10 66b42ad3
     │  my description
-    ◉  rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 ebc23d4b conflict
+    ◉  rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 cf73917d 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 08:05:10 66b42ad3
     my description
-    rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 ebc23d4b conflict
+    rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 cf73917d conflict
     my description
     rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 6fbba7bc
     my description
@@ -119,7 +119,7 @@ fn test_obslog_with_or_without_diff() {
     -bar
     ->>>>>>>
     +resolved
-    rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 ebc23d4b conflict
+    rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 cf73917d conflict
     my description
     rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 6fbba7bc
     my description
@@ -162,7 +162,7 @@ fn test_obslog_with_custom_symbols() {
     insta::assert_snapshot!(stdout, @r###"
     $  rlvkpnrz [email protected] 2001-02-03 08:05:10 66b42ad3
     │  my description
-    ┝  rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 ebc23d4b conflict
+    ┝  rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 cf73917d conflict
     │  my description
     ┝  rlvkpnrz hidden [email protected] 2001-02-03 08:05:09 6fbba7bc
     │  my description