BUG: Fix compare and continuous

asv/environment.py

@@ -890,7 +890,10 @@ def _install_project(self, repo, commit_hash, build_dir):
             # Run pip via python -m pip, avoids shebang length limit on Linux.
             # Don't run it in build directory, because it may contain Python packages
             # that pip believes to be already installed.
-            cmd = ["in-dir={env_dir} python -mpip install {wheel_file}"]
+            # --force-reinstall is needed since versions may not change between asv runs (esp. for compare)
+            # Note(rg) :: Does an implicit upgrade, but --ignore-installed can leave stale files
+            # gh-1417
+            cmd = ["in-dir={env_dir} python -mpip install {wheel_file} --force-reinstall"]
 
         if cmd:
             commit_name = repo.get_decorated_hash(commit_hash, 8)