Add mamba support to language: conda

pre_commit/languages/conda.py

@@ -1,5 +1,6 @@
 import contextlib
 import os
+import shutil
 from typing import Generator
 from typing import Sequence
 from typing import Tuple
@@ -58,15 +59,25 @@ def install_environment(
     helpers.assert_version_default('conda', version)
     directory = helpers.environment_dir(ENVIRONMENT_DIR, version)
 
+    conda_exe = None
+    if os.environ.get('PRE_COMMIT_USE_MICROMAMBA', '1') == '1':
+        conda_exe = shutil.which('micromamba')
+    if (
+        conda_exe is None and
+        os.environ.get('PRE_COMMIT_USE_MAMBA', '1') == '1'
+    ):
+        conda_exe = shutil.which('mamba')
+    conda_exe = conda_exe or 'conda'
+
     env_dir = prefix.path(directory)
     with clean_path_on_failure(env_dir):
         cmd_output_b(
-            'conda', 'env', 'create', '-p', env_dir, '--file',
+            conda_exe, 'env', 'create', '-p', env_dir, '--file',
             'environment.yml', cwd=prefix.prefix_dir,
         )
         if additional_dependencies:
             cmd_output_b(
-                'conda', 'install', '-p', env_dir, *additional_dependencies,
+                conda_exe, 'install', '-p', env_dir, *additional_dependencies,
                 cwd=prefix.prefix_dir,
             )