feat: make update-sln diff aware (#15)

* calculate the diff between current directory structure and sln representation
  - remove items from the sln that no longer exist on disk
  - add items to the sln that exist on disk and do not appear in the sln

src/scripts/update-sln

@@ -1,5 +1,17 @@
 #!/usr/bin/env bash
 
-rm -rf *.sln 1>/dev/null
-dotnet new sln
-find . -name *.csproj | xargs dotnet sln add
+__contains() { for item in "${@:2}"; do [[ "$item" == "$1" ]] && return 0; done; return 1; }
+
+for SLN in *.sln; do
+    EXISTING=($(dotnet sln "$SLN" list))
+    EXISTING=("${EXISTING[@]:2}")
+    DISCOVERED=($(find * -name '*.csproj' ! -path '*/bin/*' ! -path '*/obj/*' ! -path '*/shared/*' ))
+
+    for existing in "${EXISTING[@]}"; do
+        __contains $existing "${DISCOVERED[@]}" || dotnet sln "$SLN" remove "$existing"
+    done
+
+    for discovered in "${DISCOVERED[@]}"; do
+        __contains $discovered "${EXISTING[@]}" || dotnet sln "$SLN" add "$discovered"
+    done
+done