Implement command forgiveness with autocorrect

Similar to `git`, when a user types an unknown command like `repo tart`,
we now use `difflib.get_close_matches` to suggest similar commands.

If `help.autocorrect` is set in the git config, it will optionally
prompt the user to automatically run the assumed command, or wait
for a configured delay before executing it.

Verification Steps:
1. Created a dummy repo project locally.
2. Verified `help.autocorrect=0|false|off|no|show` suggests
   command and exits.
3. Verified `help.autocorrect=1|true|on|yes|immediate`
   automatically runs suggestion.
4. Verified `help.autocorrect=<number>` runs after
   `<number>*0.1` seconds.
5. Verified `help.autocorrect=never` exits immediately without
   suggestions.
6. Verified `help.autocorrect=prompt` asks user to accept [y/n]
   and handles correctly.

BUG: b/489753302

Change-Id: I6dcd63229cbd7badf5404459b48690c68f5b4857
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/558021
Tested-by: Sam Saccone <samccone@google.com>
Commit-Queue: Sam Saccone <samccone@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>

Author: samccone

main.py

@@ -19,6 +19,7 @@
 which takes care of execing this entry point.
 """
 
+import difflib
 import getpass
 import json
 import netrc
@@ -29,6 +30,7 @@
 import sys
 import textwrap
 import time
+from typing import Optional
 import urllib.request
 
 from repo_logging import RepoLogger
@@ -292,6 +294,102 @@ def _Run(self, name, gopts, argv):
                 result = run()
         return result
 
+    def _autocorrect_command_name(
+        self, name: str, config: RepoConfig
+    ) -> Optional[str]:
+        """Autocorrect command name based on user's git config."""
+
+        close_commands = difflib.get_close_matches(
+            name, self.commands.keys(), n=5, cutoff=0.7
+        )
+
+        if not close_commands:
+            logger.error(
+                "repo: '%s' is not a repo command.  See 'repo help'.", name
+            )
+            return None
+
+        assumed = close_commands[0]
+        autocorrect = config.GetString("help.autocorrect")
+
+        # If there are multiple close matches, git won't automatically run one.
+        # We'll always prompt instead of guessing.
+        if len(close_commands) > 1:
+            autocorrect = "prompt"
+
+        # Handle git configuration boolean values:
+        # 0, "false", "off", "no", "show": show suggestion (default)
+        # 1, "true", "on", "yes", "immediate": run suggestion immediately
+        # "never": don't run or show any suggested command
+        # "prompt": show the suggestion and prompt for confirmation
+        # positive number > 1: run suggestion after specified deciseconds
+        if autocorrect is None:
+            autocorrect = "0"
+
+        autocorrect = autocorrect.lower()
+
+        if autocorrect in ("0", "false", "off", "no", "show"):
+            autocorrect = 0
+        elif autocorrect in ("true", "on", "yes", "immediate"):
+            autocorrect = -1  # immediate
+        elif autocorrect == "never":
+            return None
+        elif autocorrect == "prompt":
+            logger.warning(
+                "You called a repo command named "
+                "'%s', which does not exist.",
+                name,
+            )
+            try:
+                resp = input(f"Run '{assumed}' instead [y/N]? ")
+                if resp.lower().startswith("y"):
+                    return assumed
+            except (KeyboardInterrupt, EOFError):
+                pass
+            return None
+        else:
+            try:
+                autocorrect = int(autocorrect)
+            except ValueError:
+                autocorrect = 0
+
+        if autocorrect != 0:
+            if autocorrect < 0:
+                logger.warning(
+                    "You called a repo command named "
+                    "'%s', which does not exist.\n"
+                    "Continuing assuming that "
+                    "you meant '%s'.",
+                    name,
+                    assumed,
+                )
+            else:
+                delay = autocorrect * 0.1
+                logger.warning(
+                    "You called a repo command named "
+                    "'%s', which does not exist.\n"
+                    "Continuing in %.1f seconds, assuming "
+                    "that you meant '%s'.",
+                    name,
+                    delay,
+                    assumed,
+                )
+                try:
+                    time.sleep(delay)
+                except KeyboardInterrupt:
+                    return None
+            return assumed
+
+        logger.error(
+            "repo: '%s' is not a repo command.  See 'repo help'.", name
+        )
+        logger.warning(
+            "The most similar command%s\n\t%s",
+            "s are" if len(close_commands) > 1 else " is",
+            "\n\t".join(close_commands),
+        )
+        return None
+
     def _RunLong(self, name, gopts, argv, git_trace2_event_log):
         """Execute the (longer running) requested subcommand."""
         result = 0
@@ -306,20 +404,22 @@ def _RunLong(self, name, gopts, argv, git_trace2_event_log):
                 outer_client=outer_client,
             )
 
-        try:
-            cmd = self.commands[name](
-                repodir=self.repodir,
-                client=repo_client,
-                manifest=repo_client.manifest,
-                outer_client=outer_client,
-                outer_manifest=outer_client.manifest,
-                git_event_log=git_trace2_event_log,
-            )
-        except KeyError:
-            logger.error(
-                "repo: '%s' is not a repo command.  See 'repo help'.", name
+        if name not in self.commands:
+            corrected_name = self._autocorrect_command_name(
+                name, outer_client.globalConfig
             )
-            return 1
+            if not corrected_name:
+                return 1
+            name = corrected_name
+
+        cmd = self.commands[name](
+            repodir=self.repodir,
+            client=repo_client,
+            manifest=repo_client.manifest,
+            outer_client=outer_client,
+            outer_manifest=outer_client.manifest,
+            git_event_log=git_trace2_event_log,
+        )
 
         Editor.globalConfig = cmd.client.globalConfig
 

tests/test_main.py

@@ -0,0 +1,166 @@
+# Copyright (C) 2026 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Tests for the main repo script and subcommand routing."""
+
+from unittest import mock
+
+import pytest
+
+from main import _Repo
+
+
+@pytest.fixture(name="repo")
+def fixture_repo():
+    repo = _Repo("repodir")
+    # Overriding the command list here ensures that we are only testing
+    # against a fixed set of commands, reducing fragility to new
+    # subcommands being added to the main repo tool.
+    repo.commands = {"start": None, "sync": None, "smart": None}
+    return repo
+
+
+@pytest.fixture(name="mock_config")
+def fixture_mock_config():
+    return mock.MagicMock()
+
+
+@mock.patch("time.sleep")
+def test_autocorrect_delay(mock_sleep, repo, mock_config):
+    """Test autocorrect with positive delay."""
+    mock_config.GetString.return_value = "10"
+
+    res = repo._autocorrect_command_name("tart", mock_config)
+
+    mock_config.GetString.assert_called_with("help.autocorrect")
+    mock_sleep.assert_called_with(1.0)
+    assert res == "start"
+
+
+@mock.patch("time.sleep")
+def test_autocorrect_delay_one(mock_sleep, repo, mock_config):
+    """Test autocorrect with '1' (0.1s delay, not immediate)."""
+    mock_config.GetString.return_value = "1"
+
+    res = repo._autocorrect_command_name("tart", mock_config)
+
+    mock_sleep.assert_called_with(0.1)
+    assert res == "start"
+
+
+@mock.patch("time.sleep", side_effect=KeyboardInterrupt())
+def test_autocorrect_delay_interrupt(mock_sleep, repo, mock_config):
+    """Test autocorrect handles KeyboardInterrupt during delay."""
+    mock_config.GetString.return_value = "10"
+
+    res = repo._autocorrect_command_name("tart", mock_config)
+
+    mock_sleep.assert_called_with(1.0)
+    assert res is None
+
+
+@mock.patch("time.sleep")
+def test_autocorrect_immediate(mock_sleep, repo, mock_config):
+    """Test autocorrect with immediate/negative delay."""
+    # Test numeric negative.
+    mock_config.GetString.return_value = "-1"
+    res = repo._autocorrect_command_name("tart", mock_config)
+    mock_sleep.assert_not_called()
+    assert res == "start"
+
+    # Test string boolean "true".
+    mock_config.GetString.return_value = "true"
+    res = repo._autocorrect_command_name("tart", mock_config)
+    mock_sleep.assert_not_called()
+    assert res == "start"
+
+    # Test string boolean "yes".
+    mock_config.GetString.return_value = "YES"
+    res = repo._autocorrect_command_name("tart", mock_config)
+    mock_sleep.assert_not_called()
+    assert res == "start"
+
+    # Test string boolean "immediate".
+    mock_config.GetString.return_value = "Immediate"
+    res = repo._autocorrect_command_name("tart", mock_config)
+    mock_sleep.assert_not_called()
+    assert res == "start"
+
+
+def test_autocorrect_zero_or_show(repo, mock_config):
+    """Test autocorrect with zero delay (suggestions only)."""
+    # Test numeric zero.
+    mock_config.GetString.return_value = "0"
+    res = repo._autocorrect_command_name("tart", mock_config)
+    assert res is None
+
+    # Test string boolean "false".
+    mock_config.GetString.return_value = "False"
+    res = repo._autocorrect_command_name("tart", mock_config)
+    assert res is None
+
+    # Test string boolean "show".
+    mock_config.GetString.return_value = "show"
+    res = repo._autocorrect_command_name("tart", mock_config)
+    assert res is None
+
+
+def test_autocorrect_never(repo, mock_config):
+    """Test autocorrect with 'never'."""
+    mock_config.GetString.return_value = "never"
+    res = repo._autocorrect_command_name("tart", mock_config)
+    assert res is None
+
+
+@mock.patch("builtins.input", return_value="y")
+def test_autocorrect_prompt_yes(mock_input, repo, mock_config):
+    """Test autocorrect with prompt and user answers yes."""
+    mock_config.GetString.return_value = "prompt"
+
+    res = repo._autocorrect_command_name("tart", mock_config)
+
+    assert res == "start"
+
+
+@mock.patch("builtins.input", return_value="n")
+def test_autocorrect_prompt_no(mock_input, repo, mock_config):
+    """Test autocorrect with prompt and user answers no."""
+    mock_config.GetString.return_value = "prompt"
+
+    res = repo._autocorrect_command_name("tart", mock_config)
+
+    assert res is None
+
+
+@mock.patch("builtins.input", return_value="y")
+def test_autocorrect_multiple_candidates(mock_input, repo, mock_config):
+    """Test autocorrect with multiple matches forces a prompt."""
+    mock_config.GetString.return_value = "10"  # Normally just delay
+
+    # 'snart' matches both 'start' and 'smart' with > 0.7 ratio
+    res = repo._autocorrect_command_name("snart", mock_config)
+
+    # Because there are multiple candidates, it should prompt
+    mock_input.assert_called_once()
+    assert res == "start"
+
+
+@mock.patch("builtins.input", side_effect=KeyboardInterrupt())
+def test_autocorrect_prompt_interrupt(mock_input, repo, mock_config):
+    """Test autocorrect with prompt and user interrupts."""
+    mock_config.GetString.return_value = "prompt"
+
+    res = repo._autocorrect_command_name("tart", mock_config)
+
+    assert res is None