Guess mistyped commands from $PATH before asking the user

When no learned correction matches, fuzzy-match the mistyped token
against executables from $PATH and shell aliases. A guess is auto-run
and recorded into the learned-corrections db only when it is
unambiguous: the token is not an existing executable, contains no
path separators or extensions, shares its first character with the
candidate, has similarity of at least 0.8, and exactly one candidate
survives. Asking the user stays the last resort.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

tests/test_learned.py

@@ -108,6 +108,58 @@ class TestGetCorrection(object):
         assert learned.get_correction("sl") == "ls"
 
 
+class TestGuessFromPath(object):
+    @pytest.fixture
+    def path_bins(self, monkeypatch):
+        def setup(executables, existing=()):
+            monkeypatch.setattr('thefuck.learned.get_all_executables',
+                                lambda: list(executables))
+            monkeypatch.setattr('thefuck.learned.which',
+                                lambda token: token in existing)
+        return setup
+
+    def test_guesses_unique_close_match(self, learned, path_bins):
+        path_bins(executables=['clear', 'grep', 'sed'])
+        assert learned.guess_from_path('cler') == 'clear'
+
+    def test_keeps_arguments(self, learned, path_bins):
+        path_bins(executables=['python', 'pydoc', 'grep'])
+        assert (learned.guess_from_path('pyhton script.py')
+                == 'python script.py')
+
+    def test_returns_none_when_ambiguous(self, learned, path_bins):
+        path_bins(executables=['clear', 'clean'])
+        assert learned.guess_from_path('clea') is None
+
+    def test_returns_none_when_token_is_executable(self, learned, path_bins):
+        path_bins(executables=['clear'], existing=['clear'])
+        assert learned.guess_from_path('clear') is None
+
+    def test_returns_none_for_path_like_token(self, learned, path_bins):
+        path_bins(executables=['git', 'grep', 'sed'])
+        assert learned.guess_from_path('./gti push') is None
+
+    def test_returns_none_for_token_with_extension(self, learned, path_bins):
+        path_bins(executables=['git', 'grep', 'sed'])
+        assert learned.guess_from_path('giti.py x') is None
+
+    def test_returns_none_when_first_char_differs(self, learned, path_bins):
+        path_bins(executables=['top'])
+        assert learned.guess_from_path('htop') is None
+
+    def test_returns_none_below_cutoff(self, learned, path_bins):
+        path_bins(executables=['grep', 'sed', 'awk'])
+        assert learned.guess_from_path('total') is None
+
+    def test_guesses_after_sudo(self, learned, path_bins):
+        path_bins(executables=['clear', 'grep', 'sed'])
+        assert learned.guess_from_path('sudo cler') == 'sudo clear'
+
+    def test_returns_none_for_empty_script(self, learned, path_bins):
+        path_bins(executables=['git'])
+        assert learned.guess_from_path('') is None
+
+
 class TestClear(object):
     def test_removes_all_entries(self, learned):
         learned.record("git psuh", "git push")