[internal] Document how to regenerate lockfiles until we have more ro…

…bust automatic support (#12386)

In the meantime to landing #12382, this makes things more clear for pantsbuild/pants contributors.

Of course, this PR is not sustainable, but it brings some clarity while we iterate on this volatile code.

[ci skip-rust]
[ci skip-build-wheels]

3rdparty/python/lockfile.txt

@@ -1,4 +1,7 @@
 #
+# To regenerate, run `./pants --tag=-lockfile_ignore lock ::` on a machine w/ Py37.
+#
+#
 # This file is autogenerated by pip-compile with python 3.7
 # To update, run:
 #

src/python/pants/backend/awslambda/python/lambdex_lockfile.txt

@@ -1,4 +1,7 @@
 #
+# To regenerate, run `./pants tool-lock` on a machine w/ Py36.
+#
+#
 # This file is autogenerated by pip-compile with python 3.6
 # To update, run:
 #

src/python/pants/backend/codegen/protobuf/python/mypy_protobuf_lockfile.txt

@@ -1,4 +1,7 @@
 #
+# To regenerate, run `./pants tool-lock` on a machine w/ Py36.
+#
+#
 # This file is autogenerated by pip-compile with python 3.6
 # To update, run:
 #

src/python/pants/backend/python/lint/black/lockfile.txt

@@ -1,4 +1,8 @@
 #
+# To regenerate, run `./pants tool-lock` on a machine w/ Py36.
+# You MUST manually add back the `python_version` environment markers. (This will be automated soon.)
+#
+#
 # This file is autogenerated by pip-compile with python 3.6
 # To update, run:
 #

src/python/pants/backend/python/lint/docformatter/lockfile.txt

@@ -1,4 +1,7 @@
 #
+# To regenerate, run `./pants tool-lock` on a machine w/ Py36.
+#
+#
 # This file is autogenerated by pip-compile with python 3.6
 # To update, run:
 #

src/python/pants/backend/python/lint/isort/lockfile.txt

@@ -1,4 +1,7 @@
 #
+# To regenerate, run `./pants tool-lock` on a machine w/ Py36.
+#
+#
 # This file is autogenerated by pip-compile with python 3.6
 # To update, run:
 #

src/python/pants/backend/python/lint/yapf/lockfile.txt

@@ -1,4 +1,7 @@
 #
+# To regenerate, run `./pants tool-lock` on a machine w/ Py36.
+#
+#
 # This file is autogenerated by pip-compile with python 3.6
 # To update, run:
 #

src/python/pants/backend/python/subsystems/coverage_py_lockfile.txt

@@ -1,4 +1,7 @@
 #
+# To regenerate, run `./pants tool-lock` on a machine w/ Py37.
+#
+#
 # This file is autogenerated by pip-compile with python 3.7
 # To update, run:
 #