chore: split out flake8 dependencies into their own file

This is to make it possible to run a GitHub action for flake8 that
doesn't need to load all of requirements-dev.txt.

Author: mhucka

requirements-dev.txt

@@ -5,20 +5,12 @@
 # @website https://github.com/caltechlibrary/iga
 
 -r requirements.txt
+-r requirements-lint.txt
 
 pytest      >= 6.2.5
 pytest-cov  >= 3.0.0
 pytest-mock >= 3.7.0
 
-flake8                     >= 4.0.1
-flake8-bugbear             >= 22.4.25
-flake8-builtins            >= 1.5.3
-flake8-comprehensions      >= 3.8.0
-flake8-executable          >= 2.1.1
-flake8_implicit_str_concat >= 0.3.0
-flake8-pie                 >= 0.15.0
-flake8-simplify            >= 0.19.2
-
 twine
 wheel
 

requirements-lint.txt

@@ -0,0 +1,19 @@
+# @file    requirements-lint.txt
+# @brief   Python dependencies for linting the codebase
+# @created 2023-07-24
+# @license Please see the file named LICENSE in the project directory
+# @website https://github.com/caltechlibrary/iga
+#
+# This set of dependencies is split out from requirements-dev.txt so that
+# GitHub Actions can load just this subset and not all the other
+# requirements. (IGA has a huge list of requirements and they take a long
+# time to install -- a needless waste of time when only running flake8.)
+
+flake8                     >= 4.0.1
+flake8-bugbear             >= 22.4.25
+flake8-builtins            >= 1.5.3
+flake8-comprehensions      >= 3.8.0
+flake8-executable          >= 2.1.1
+flake8_implicit_str_concat >= 0.3.0
+flake8-pie                 >= 0.15.0
+flake8-simplify            >= 0.19.2