notes on tagging added and more cleanup

- notes on tagging added
- backport of 2e2a6ff (__pycache__ removal)

doc/howto_release.md

@@ -77,6 +77,7 @@ find . -name '*.rej'  | xargs rm
 find . -name '*.o'    | xargs rm
 find . -name '*.pyc'  | xargs rm
 find . -name 'OBJ.*'  | xargs rm -r
+find . -name '__pycache__' | xargs rm -r
 rm -f gui/wxpython/menustrings.py gui/wxpython/build_ext.pyc gui/wxpython/xml/menudata.xml gui/wxpython/xml/module_tree_menudata.xml
 chmod -R a+r *
 ```
@@ -149,6 +150,14 @@ To be done in GH interface:
 
 https://github.com/OSGeo/grass/releases/new
 
+Tag version | target (examples):
+  7.8.1RC1  | releasebranch_7_8
+
+Add release desciption (re-use existing texts as possible)
+
+If RC, then check
+[x] This is a pre-release
+
 ### Packaging of source code tarball
 
 TODO: add checkout of code via release tag (?)
@@ -193,6 +202,8 @@ Example:
 2019
 ```
 
+Commit as "back to dev"
+
 Reset local copy to GH:
 ```bash
 # update from GH