Implement concurrent execution of individual hooks

pre_commit/languages/docker.py

@@ -97,4 +97,8 @@ def run_hook(prefix, hook, file_args):  # pragma: windows no cover
 
     entry_tag = ('--entrypoint', entry_exe, docker_tag(prefix))
     cmd = docker_cmd() + entry_tag + cmd_rest
-    return xargs(cmd, file_args)
+    return xargs(
+        cmd,
+        file_args,
+        target_concurrency=helpers.target_concurrency(hook),
+    )

pre_commit/languages/docker_image.py

@@ -16,4 +16,8 @@ install_environment = helpers.no_install
 def run_hook(prefix, hook, file_args):  # pragma: windows no cover
     assert_docker_available()
     cmd = docker_cmd() + helpers.to_cmd(hook)
-    return xargs(cmd, file_args)
+    return xargs(
+        cmd,
+        file_args,
+        target_concurrency=helpers.target_concurrency(hook),
+    )

pre_commit/languages/golang.py

@@ -81,4 +81,8 @@ def install_environment(prefix, version, additional_dependencies):
 
 def run_hook(prefix, hook, file_args):
     with in_env(prefix):
-        return xargs(helpers.to_cmd(hook), file_args)
+        return xargs(
+            helpers.to_cmd(hook),
+            file_args,
+            target_concurrency=helpers.target_concurrency(hook),
+        )

pre_commit/languages/helpers.py

@@ -1,5 +1,6 @@
 from __future__ import unicode_literals
 
+import multiprocessing
 import shlex
 
 from pre_commit.util import cmd_output
@@ -45,3 +46,11 @@ def basic_healthy(prefix, language_version):
 
 def no_install(prefix, version, additional_dependencies):
     raise AssertionError('This type is not installable')
+
+
+def target_concurrency(hook):
+    if hook['require_serial']:
+        return 1
+    else:
+        # TODO: something smart!
+        return multiprocessing.cpu_count()

pre_commit/languages/node.py

@@ -71,4 +71,8 @@ def install_environment(prefix, version, additional_dependencies):
 
 def run_hook(prefix, hook, file_args):
     with in_env(prefix, hook['language_version']):
-        return xargs(helpers.to_cmd(hook), file_args)
+        return xargs(
+            helpers.to_cmd(hook),
+            file_args,
+            target_concurrency=helpers.target_concurrency(hook),
+        )

pre_commit/languages/python.py

@@ -127,7 +127,11 @@ def py_interface(_dir, _make_venv):
 
     def run_hook(prefix, hook, file_args):
         with in_env(prefix, hook['language_version']):
-            return xargs(helpers.to_cmd(hook), file_args)
+            return xargs(
+                helpers.to_cmd(hook),
+                file_args,
+                target_concurrency=helpers.target_concurrency(hook),
+            )
 
     def install_environment(prefix, version, additional_dependencies):
         additional_dependencies = tuple(additional_dependencies)

pre_commit/languages/ruby.py

@@ -126,4 +126,8 @@ def install_environment(
 
 def run_hook(prefix, hook, file_args):  # pragma: windows no cover
     with in_env(prefix, hook['language_version']):
-        return xargs(helpers.to_cmd(hook), file_args)
+        return xargs(
+            helpers.to_cmd(hook),
+            file_args,
+            target_concurrency=helpers.target_concurrency(hook),
+        )

pre_commit/languages/rust.py

@@ -91,4 +91,8 @@ def install_environment(prefix, version, additional_dependencies):
 
 def run_hook(prefix, hook, file_args):
     with in_env(prefix):
-        return xargs(helpers.to_cmd(hook), file_args)
+        return xargs(
+            helpers.to_cmd(hook),
+            file_args,
+            target_concurrency=helpers.target_concurrency(hook),
+        )

pre_commit/languages/script.py

@@ -13,4 +13,8 @@ install_environment = helpers.no_install
 def run_hook(prefix, hook, file_args):
     cmd = helpers.to_cmd(hook)
     cmd = (prefix.path(cmd[0]),) + cmd[1:]
-    return xargs(cmd, file_args)
+    return xargs(
+        cmd,
+        file_args,
+        target_concurrency=helpers.target_concurrency(hook),
+    )

pre_commit/languages/swift.py

@@ -53,4 +53,8 @@ def install_environment(
 
 def run_hook(prefix, hook, file_args):  # pragma: windows no cover
     with in_env(prefix):
-        return xargs(helpers.to_cmd(hook), file_args)
+        return xargs(
+            helpers.to_cmd(hook),
+            file_args,
+            target_concurrency=helpers.target_concurrency(hook),
+        )

pre_commit/languages/system.py

@@ -11,4 +11,8 @@ install_environment = helpers.no_install
 
 
 def run_hook(prefix, hook, file_args):
-    return xargs(helpers.to_cmd(hook), file_args)
+    return xargs(
+        helpers.to_cmd(hook),
+        file_args,
+        target_concurrency=helpers.target_concurrency(hook),
+    )