Add CI and username factors

Author: jayvdb

README.md

@@ -7,7 +7,22 @@ Any factor can be added with `--prepend-factor` and `--append-factor`.
 The added factors can be combined with the `-e` argument and
 `TOXENV` environment variable.
 
+## CI factors
+
+The argument `add-ci-factor` will detect the CI from the list below and add
+it as a factor or fallback to adding "ci":
+
+- appveyor
+- cirrusci
+- travis
+
+To always add a "ci" factor, use `--append-factor=ci`.
+
+Many CI services use a username which are the name of the service name.
+For those services, the `--prepend-username-factor` may be helpful.
+
 ## Platform factors
+
 Three specific factors can be added to simplify selecting OS and arch:
 The following example depends on `--prepend-ostype-factor`
 
@@ -29,7 +44,8 @@ is ever fixed.
 The factors `--prepend-cpuarch-factor` and `--prepend-archraw-factor`
 are provided by https://github.com/workhorsy/py-cpuinfo .
 
-The cpuarch factor currently only supports
+The cpuarch factor currently only supports:
+
 - x86_32
 - x86_64
 - arm_7

tox_add_factor/hooks.py

@@ -1,7 +1,8 @@
 """Tox hook implementations."""
 from __future__ import print_function
+
 import os
-import sys
+
 import tox
 
 try:
@@ -39,6 +40,18 @@ def tox_addoption(parser):
         help="Prepend OS type to factors, such as linux, macos, windows.",
     )
 
+    parser.add_argument(
+        "--prepend-username-factor",
+        action="store_true",
+        help="Prepend username to factors.",
+    )
+
+    parser.add_argument(
+        "--add-ci-factor",
+        action="store_true",
+        help="Add CI factors if environment variable is set, such as appveyor, travis or fallback ci.",
+    )
+
 
 @tox.hookimpl(trylast=True)
 def tox_configure(config):
@@ -76,6 +89,33 @@ def tox_configure(config):
         else:
             config.option.prepend_factor.insert(0, _get_os_type().lower())
 
+    if config.option.add_ci_factor and "CI" in os.environ:
+        extra_factor = None
+        if "APPVEYOR" in os.environ or "TRAVIS" in os.environ:
+            config.option.prepend_username_factor = True
+        elif "CIRRUS_CI" in os.environ:
+            extra_factor = "cirrusci"
+        else:
+            extra_factor = "ci"
+
+        if extra_factor:
+            if not config.option.append_factor:
+                config.option.append_factor = [extra_factor]
+            else:
+                config.option.append_factor.insert(0, extra_factor)
+
+    if config.option.prepend_username_factor:
+        import getpass  # noqa
+
+        username = getpass.getuser()
+        if username:
+            username = username.lower()
+
+        if not config.option.prepend_factor:
+            config.option.prepend_factor = [username]
+        else:
+            config.option.prepend_factor.insert(0, username)
+
     if config.option.prepend_factor:
         add_factors(config, config.option.prepend_factor, position=BEFORE)
     if config.option.append_factor: