cli: implement enough of jj fix to run a single tool on all files

CHANGELOG.md

@@ -58,6 +58,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * Upgraded `scm-record` from v0.2.0 to v0.3.0. See release notes at https://github.com/arxanas/scm-record/releases/tag/v0.3.0
 
+* New command `jj fix` that can be configured to update commits by running code
+  formatters (or similar tools) on changed files. The configuration schema and
+  flags are minimal for now, with a number of improvements planned (for example,
+  [#3800](https://github.com/martinvonz/jj/issues/3800) and
+  [#3801](https://github.com/martinvonz/jj/issues/3801)).
+
 ### Fixed bugs
 
 * Previously, `jj git push` only made sure that the branch is in the expected

cli/Cargo.toml

@@ -75,6 +75,7 @@ once_cell = { workspace = true }
 pest = { workspace = true }
 pest_derive = { workspace = true }
 pollster = { workspace = true }
+rayon = { workspace = true }
 regex = { workspace = true }
 rpassword = { workspace = true }
 scm-record = { workspace = true }

cli/src/commands/mod.rs

@@ -93,7 +93,6 @@ enum Command {
     Duplicate(duplicate::DuplicateArgs),
     Edit(edit::EditArgs),
     Files(files::FilesArgs),
-    #[command(hide = true)]
     Fix(fix::FixArgs),
     #[command(subcommand)]
     Git(git::GitCommand),

cli/src/config-schema.json

@@ -482,6 +482,19 @@
                     "additionalProperties": true
                 }
             }
+        },
+	"fix": {
+            "type": "object",
+            "description": "Settings for jj fix",
+            "properties": {
+                "tool-command": {
+                    "type": "array",
+                    "items": {
+                        "type": "string"
+                    },
+                    "description": "Shell command that takes file content on stdin and returns fixed file content on stdout"
+                }
+            }
         }
     }
 }

cli/tests/cli-reference@.md.snap

@@ -37,6 +37,7 @@ This document contains the help content for the `jj` command-line program.
 * [`jj duplicate`↴](#jj-duplicate)
 * [`jj edit`↴](#jj-edit)
 * [`jj files`↴](#jj-files)
+* [`jj fix`↴](#jj-fix)
 * [`jj git`↴](#jj-git)
 * [`jj git remote`↴](#jj-git-remote)
 * [`jj git remote add`↴](#jj-git-remote-add)
@@ -117,6 +118,7 @@ To get started, see the tutorial at https://github.com/martinvonz/jj/blob/main/d
 * `duplicate` — Create a new change with the same content as an existing one
 * `edit` — Sets the specified revision as the working-copy revision
 * `files` — List files in a revision
+* `fix` — Update files with formatting fixes or other changes
 * `git` — Commands for working with Git remotes and the underlying Git repo
 * `init` — Create a new repo in the given directory
 * `interdiff` — Compare the changes of two commits
@@ -758,6 +760,44 @@ List files in a revision
 
 
 
+## `jj fix`
+
+Update files with formatting fixes or other changes
+
+The primary use case for this command is to apply the results of automatic
+code formatting tools to revisions that may not be properly formatted yet.
+It can also be used to modify files with other tools like `sed` or `sort`.
+
+The changed files in the given revisions will be updated with any fixes
+determined by passing their file content through the external tool.
+Descendants will also be updated by passing their versions of the same files
+through the same external tool, which will never result in new conflicts.
+Files with existing conflicts will be updated on all sides of the conflict,
+which can potentially increase or decrease the number of conflict markers.
+
+The external tool must accept the current file content on standard input,
+and return the updated file content on standard output. The output will not
+be used unless the tool exits with a successful exit code. Output on
+standard error will be passed through to the terminal.
+
+The configuration schema is expected to change in the future. For now, it
+defines a single command that will affect all changed files in the specified
+revisions. For example, to format some Rust code changed in the working copy
+revision, you could write this configuration:
+
+[fix]
+tool-command = ["rustfmt", "--emit", "stdout"]
+
+And then run the command `jj fix -s @`.
+
+**Usage:** `jj fix [OPTIONS]`
+
+###### **Options:**
+
+* `-s`, `--source <SOURCE>` — Fix files in the specified revision(s) and their descendants
+
+
+
 ## `jj git`
 
 Commands for working with Git remotes and the underlying Git repo

cli/tests/runner.rs

@@ -27,6 +27,7 @@ mod test_diff_command;
 mod test_diffedit_command;
 mod test_duplicate_command;
 mod test_edit_command;
+mod test_fix_command;
 mod test_generate_md_cli_help;
 mod test_git_clone;
 mod test_git_colocated;