docker: fix unexpected package version due to incomplete work tree

.dockerignore

@@ -1,4 +1,9 @@
-*
-!./.git
-!./pyftpd_sink
-!./setup.py
+*.swp
+/*.egg-info/
+/.eggs/
+/.pytest_cache/
+/Pipfile
+/Pipfile.lock
+/__pycache__/
+/build/
+/dist/

.gitignore

@@ -1 +1,2 @@
+.*.swp
 /dist

Dockerfile

@@ -15,7 +15,7 @@ ENV FTP_PASSIVE_PORT 62121
 EXPOSE $FTP_CONTROL_PORT $FTP_PASSIVE_PORT
 
 COPY . /pyftpd-sink
-RUN pip install --user --upgrade /pyftpd-sink
+RUN pip install --user /pyftpd-sink
 
 # TODO set masquerade address for passive mode
 CMD ["pyftpd-sink", "--root-dir", "/sink"]