feat: support (skip) commented lines in version-file

Sometimes it is convenient to be able to temporarily disable something
in a version-file. Because these files often aren't necessarily tracked
in a SCM, especially when working with virtualenvs, the SCM diffs won't
help with showing removed lines which are currently the only way to
disable something.

README.md

@@ -136,6 +136,7 @@ executable path to each of these using `pyenv which`, e.g. `pyenv which python2.
 (should display `$(pyenv root)/versions/2.5/bin/python2.5`), or `pyenv which
 python3.4` (should display path to system Python3). You can also specify multiple
 versions in a `.python-version` file, separated by newlines or any whitespace.
+Lines starting with a `#` are ignored.
 
 ### Locating the Python Installation
 

libexec/pyenv-version-file-read

@@ -9,7 +9,7 @@ if [ -e "$VERSION_FILE" ]; then
   # Read the first non-whitespace word from the specified version file.
   # Be careful not to load it whole in case there's something crazy in it.
   IFS="${IFS}"$'\r'
-  words=($(cut -b 1-1024 "$VERSION_FILE" | sed 's/[[:space:]]*\([^[:space:]^[:space:]]*\).*/\1/'))
+  words=($(cut -b 1-1024 "$VERSION_FILE" | sed -n 's/^[[:space:]]*\([^[:space:]#][^[:space:]]*\).*/\1/p'))
   versions=("${words[@]}")
 
   if [ -n "$versions" ]; then

test/version-file-read.bats

@@ -70,3 +70,15 @@ IN
   run pyenv-version-file-read my-version
   assert_success "3.3.5"
 }
+
+@test "skips comment lines" {
+  cat > my-version <<IN
+3.9.3
+3.8.9
+  # 3.4.0
+#3.3.7
+2.7.16
+IN
+  run pyenv-version-file-read my-version
+  assert_success "3.9.3:3.8.9:2.7.16"
+}