Explain with comments to make maintenance easier

test/integration/Dockerfile

@@ -14,38 +14,53 @@ COPY test/integration/docker/*.sh .
 RUN git config --global user.email "[email protected]" && \
     git config --global user.name "dev"
 
+#
+# Directory to place the source code of remer.
+# Used to build and install the gem file of remer.
+#
 RUN mkdir /remer-src && \
     git config --global safe.directory /remer-src
 
-WORKDIR /git-repos
+#
+# Pseudo remote repositories for test plugins and themes
+#
+WORKDIR /git-server-repos
 RUN git init --bare plugin_a.git
 RUN git init --bare theme_a.git
 
-WORKDIR /tmp
+#
+# Local repositories to maintain test plugins and themes
+#
+WORKDIR /git-local-repos
 COPY test/integration/docker/plugin_a plugin_a
 COPY test/integration/docker/theme_a theme_a
 
-WORKDIR /tmp/plugin_a
+# Plugin A
+WORKDIR /git-local-repos/plugin_a
 RUN git init && \
-    git remote add origin /git-repos/plugin_a.git && \
+    git remote add origin /git-server-repos/plugin_a.git && \
     git add . && git commit -m "commit" && git push origin master && \
     git tag -a v0.1.0 -m "v0.1.0" && git push origin v0.1.0 && \
     git switch -c stable && git push origin stable
-
-WORKDIR /tmp/theme_a
+# Theme A
+WORKDIR /git-local-repos/theme_a
 RUN git init && \
-    git remote add origin /git-repos/theme_a.git && \
+    git remote add origin /git-server-repos/theme_a.git && \
     git add . && git commit -m "commit" && git push origin master
 
+#
+# Redmine
+#
 WORKDIR /redmine
 RUN git clone --depth 1 https://github.com/redmine/redmine.git .
-
 COPY test/integration/docker/database.yml config/database.yml
 
+# Directory for the bundle cache
 RUN mkdir /redmine-bundle
 VOLUME /redmine-bundle
 ENV BUNDLE_PATH=/redmine-bundle
 
+# Definition file
 COPY test/integration/docker/extensions.rb .extensions.rb
 
 RUN bundle install && bin/rails db:prepare