Added spell-checking to CI: Check whether change increases number of mistakes.

Closes #53 (closed)

doc.zih.tu-dresden.de/util/check-spelling-changes.sh

+#!/bin/bash
+
+set -euo pipefail
+
+scriptpath=${BASH_SOURCE[0]}
+basedir=`dirname "$scriptpath"`
+basedir=`dirname "$basedir"`
+wordlistfile=$basedir/wordlist.aspell
+
+function getNumberOfAspellOutputLines(){
+  cat - | aspell -p "$wordlistfile" --ignore 2 -l en_US list | sort -u | wc -l
+}
+
+branch="preview"
+if [ -n "$CI_MERGE_REQUEST_TARGET_BRANCH_NAME" ]; then
+    branch="origin/$CI_MERGE_REQUEST_TARGET_BRANCH_NAME"
+fi
+
+any_fails=false
+
+source_hash=`git merge-base HEAD "$branch"`
+files=$(git diff --name-only "$source_hash")
+for f in $files; do
+    if [ "${f: -3}" == ".md" ]; then
+        previous_count=`git show "$source_hash:$f" | getNumberOfAspellOutputLines`
+        current_count=`cat "$f" | getNumberOfAspellOutputLines`
+        if [ $current_count -gt $previous_count ]; then
+            echo "-- File $f"
+            echo "Change increases spelling mistake count (from $previous_count to $current_count)"
+            any_fails=true
+        fi
+    fi
+done
+
+if [ "$any_fails" == true ]; then
+    exit 1
+fi