deploy both the latest and specified older version of salsa book

book/_redirects

@@ -0,0 +1,2 @@
+# Redirects from what the browser requests to what we serve
+/                /salsa2022

book/netlify.sh

@@ -13,4 +13,34 @@ curl -L https://github.com/badboy/mdbook-mermaid/releases/download/v$MDBOOK_MERM
 curl -L https://github.com/Michael-F-Bryan/mdbook-linkcheck/releases/download/v$MDBOOK_LINKCHECK_VERSION/mdbook-linkcheck.v$MDBOOK_LINKCHECK_VERSION.x86_64-unknown-linux-gnu.zip -O
 unzip mdbook-linkcheck.v$MDBOOK_LINKCHECK_VERSION.x86_64-unknown-linux-gnu.zip -d ~/.cargo/bin
 chmod +x ~/.cargo/bin/mdbook-linkcheck
-mdbook build
+
+# ======================================================================
+# The following script automates the deployment of both the latest and a
+# specified older version of the 'salsa' documentation using mdbook
+
+# Store the current branch or commit
+original_branch=$(git rev-parse --abbrev-ref HEAD)
+if [ "$original_branch" == "HEAD" ]; then
+  original_branch=$(git rev-parse HEAD)
+fi
+
+mkdir -p versions  # Create a root directory for all versions
+
+# Declare an associative array to map commits to custom version directory names
+declare -A commit_to_version=( ["$original_branch"]="salsa2022" ["754eea8b5f8a31b1100ba313d59e41260b494225"]="salsa" )
+
+# Loop over the keys (commit hashes or branch names) in the associative array
+for commit in "${!commit_to_version[@]}"; do
+  git checkout $commit
+  mdbook build
+  version_dir="versions/${commit_to_version[$commit]}"
+  mkdir -p $version_dir
+  mv book/html/* $version_dir
+  rm -rf book
+done
+
+# Return to the original branch or commit
+git checkout $original_branch
+
+# Copy _redirects to the root directory
+cp _redirects versions