Added the Dockerfile.

Dockerfile

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+FROM archlinux/base
+
+# The default mirrors in archlinux/base are slow and undependable. They
+# frequently fail to download packages, hence the until statement to keep
+# running until the update and install of reflector succeeds. The mirrors are
+# sorted base on their 'rate'.
+ENV UPDATE_MIRROR_ATTEMPTS=0
+RUN until \
+        yes | pacman -Sy && \
+        \
+        # Install reflector, which is a tool for creating a pacman mirrorlist,
+        pacman -S --noconfirm reflector && \
+        \
+        # Backup the current mirrorlist just in case.
+        # TODO This shouldn't be inside the until loop.
+        # TODO Just the first 2 commands should be in this until loop.
+        cp /etc/pacman.d/mirrorlist /etc/pacman.d/mirrorlist.backup && \
+        \
+        # Create a new mirrorlist by sorting the last 50 mirrors to sync and
+        # sort them by the download 'rate'.
+        # TODO Make the number of mirrors configurable.
+        reflector \
+            --verbose \
+            --latest 50 \
+            --sort rate \
+            --save /etc/pacman.d/mirrorlist || \
+        \
+        # This only runs if one of the previous commands failed. Therefore, we
+        # increment the the attempt counter.
+        ((UPDATE_MIRROR_ATTEMPTS > 5)); \
+    do \
+        echo -e "\n\nFailed attempt number $((UPDATE_MIRROR_ATTEMPTS+1)) to" \
+                "update the mirrorlist. Trying again.\n\n"; \
+        ((UPDATE_MIRROR_ATTEMPTS=UPDATE_MIRROR_ATTEMPTS+1)); \
+    done && \
+    \
+    # Remove the reflector package and the package cache.
+    pacman -Rns --noconfirm reflector
+
+    # I was going to run this or paccache, however it looks like we've only
+    # added ~7MB. The cache looks to be empty.
+    #pacman -Scc --noconfirm
+