build scripts to have proper math in markdown

a pre-commit hook that checks if $ $ without ` exists and a script that introduces the ` where necessary

scripts/pre-commit

+#!/bin/bash
+
+set -e
+
+# If we have a STDIN, use it, otherwise get one
+if tty >/dev/null 2>&1; then
+    TTY=$(tty)
+else
+    TTY=/dev/tty
+fi
+
+IFS=$'\n'
+
+# http://djm.me/ask
+ask() {
+    while true; do
+
+        if [ "${2:-}" = "Y" ]; then
+            prompt="Y/n"
+            default=Y
+        elif [ "${2:-}" = "N" ]; then
+            prompt="y/N"
+            default=N
+        else
+            prompt="y/n"
+            default=
+        fi
+
+        # Ask the question (not using "read -p" as it uses stderr not stdout)
+        echo -n "$1 [$prompt] "
+
+        # Read the answer
+        read REPLY < "$TTY"
+
+        # Default?
+        if [ -z "$REPLY" ]; then
+            REPLY=$default
+        fi
+
+        # Check if the reply is valid
+        case "$REPLY" in
+            Y*|y*) return 0 ;;
+            N*|n*) return 1 ;;
+        esac
+
+    done
+}
+
+check_file() {
+    local file="$1"
+    local match_pattern="$2"
+
+    local file_changes_with_context=$(git diff -U999999999 -p --cached --color=always -- "${file}")
+
+    # From the diff, get the green lines starting with '+' and including '$match_pattern'
+    local matched_additions=$(echo "$file_changes_with_context" | grep -C1 $'^\e\\[32m\+.*'"$match_pattern")
+
+    if [ -n "$matched_additions" ]; then
+        echo -e "\n$file additions match '$match_pattern':\n"
+
+        for matched_line in $matched_additions
+        do
+            echo "$matched_line"
+        done
+
+        if ask "Include this in your commit?"; then
+            echo 'Including'
+        else
+            echo "Not committing, because $file matches $match_pattern"
+            exit 1
+        fi
+    fi
+}
+
+# Actual hook logic:
+
+for file in $(git diff --cached -p --name-status | cut -c3-); do
+  case "${file}" in
+    *.md) echo "check file ${file}"
+      check_file "${file}" '[^`]\$[^$`]*\$' ;;
+  esac
+done
+exit

scripts/repairgitlabmathmd.sh

+#! /usr/bin/env sh
+# gitlab marks math with $`  `$. I often forget the backticks
+# so this script should add them
+for i in $(find .maindir/notes -type f -name "*.md")
+  # -type f means regular file. Without it, the symbolic links are changed to regular files by sed
+  do
+    sed -i 's#\([^`]\|^\)\$\([^$`]\+\)\$#\1\$`\2`\$#g' "${i}"
+    # \(      # the symbol in front of the math is captured (-> \1)
+    #   [^`]  # if it is `, then we are looking at text behind a math env, so it should not be matched
+    #   |^    # but it is OK if there is nothing but the beginning of the line
+    # \)
+    # \$      # without \, the $ is a special symbol for the beginning of a line
+    # \(      # the actual math content needs to be captured
+    #   [^$`]\+  # sed regexp is greedy, taking the end of the math until the end of the last math in the line if we didn't forbid $ and ` (if the content has `, then it's already fine)
+    # \)
+    # \$     # the closing $
+  done