Add new ecosystem comparison modes for the formatter (#8416)

Previously, the ecosystem checks formatted with the baseline then
formatted again with `--diff` to get the changed files.

Now, the ecosystem checks support a new mode where we:
- Format with the baseline
- Commit the changes
- Reset to the target ref
- Format again
- Check the diff from the baseline commit

This effectively tests Ruff changes on unformatted code rather than
changes in previously formatted code (unless, of course, the project is
already using Ruff).

While this mode is the new default, I've retained the old one for local
checks. The mode can be toggled with `--format-comparison <type>`.

Includes some more aggressive resetting of the GitHub repositories when
cached.

Here, I've also stubbed comparison modes in which `black` is used as the
baseline. While these do nothing here, #8419 adds support.

I tested this with the commit from #8216 and ecosystem changes appear
https://gist.github.com/zanieb/a982ec8c392939043613267474471a6e

python/ruff-ecosystem/ruff_ecosystem/cli.py

@@ -12,6 +12,7 @@ from signal import SIGINT, SIGTERM
 
 from ruff_ecosystem import logger
 from ruff_ecosystem.defaults import DEFAULT_TARGETS
+from ruff_ecosystem.format import FormatComparison
 from ruff_ecosystem.main import OutputFormat, main
 from ruff_ecosystem.projects import RuffCommand
 
@@ -77,6 +78,12 @@ def entrypoint():
     if args.force_preview:
         targets = [target.with_preview_enabled() for target in targets]
 
+    format_comparison = (
+        FormatComparison(args.format_comparison)
+        if args.ruff_command == RuffCommand.format.value
+        else None
+    )
+
     with cache_context as cache:
         loop = asyncio.get_event_loop()
         main_task = asyncio.ensure_future(
@@ -88,6 +95,7 @@ def entrypoint():
                 format=OutputFormat(args.output_format),
                 project_dir=Path(cache),
                 raise_on_failure=args.pdb,
+                format_comparison=format_comparison,
             )
         )
         # https://stackoverflow.com/a/58840987/3549270
@@ -120,7 +128,7 @@ def parse_args() -> argparse.Namespace:
     )
     parser.add_argument(
         "--output-format",
-        choices=[option.name for option in OutputFormat],
+        choices=[option.value for option in OutputFormat],
         default="markdown",
         help="Location for caching cloned repositories",
     )
@@ -140,9 +148,15 @@ def parse_args() -> argparse.Namespace:
         action="store_true",
         help="Force preview mode to be enabled for all projects",
     )
+    parser.add_argument(
+        "--format-comparison",
+        choices=[option.value for option in FormatComparison],
+        default=FormatComparison.ruff_and_ruff,
+        help="Type of comparison to make when checking formatting.",
+    )
     parser.add_argument(
         "ruff_command",
-        choices=[option.name for option in RuffCommand],
+        choices=[option.value for option in RuffCommand],
         help="The Ruff command to test",
     )
     parser.add_argument(