release.py: Follow-up to r1800225.
* tools/dist/release.py
(clean_dist): Don't remove 1.8.19 artifacts when 1.9.7 and 1.10.0-alpha3 are
present.  Leave a note about an edge case that currently requires manual
intervention once every two years.
@@ -874,7 +874,9 @@ def clean_dist(args):
versions = set(map(Version, filenames))
minor_lines = set(map(minor, versions))
to_keep = set()
- for recent_line in sorted(minor_lines, reverse=True)[:2]:
+ # Keep 3 minor lines: 1.10.0-alpha3, 1.9.7, 1.8.19.
+ # TODO: When we release 1.A.0 GA we'll have to manually remove 1.(A-2).* artifacts.
+ for recent_line in sorted(minor_lines, reverse=True)[:3]:
to_keep.add(max(
x for x in versions
if minor(x) == recent_line
