Improve add-release-channel, fixes #708

app/ghcup/GHCup/OptParse/Config.hs

@@ -188,9 +188,15 @@ config configCommand settings keybindings runLogger = case configCommand of
       AddSource xs -> do
         doConfig (defaultUserSettings { uUrlSource = Just $ AddSource (xs <> [Right uri]) })
         pure ExitSuccess
-      _ -> do
+      GHCupURL -> do
         doConfig (defaultUserSettings { uUrlSource = Just $ AddSource [Right uri] })
         pure ExitSuccess
+      OwnSource xs -> do
+        doConfig (defaultUserSettings { uUrlSource = Just $ OwnSource (xs <> [Right uri]) })
+        pure ExitSuccess
+      OwnSpec spec -> do
+        doConfig (defaultUserSettings { uUrlSource = Just $ OwnSource ([Left spec, Right uri]) })
+        pure ExitSuccess
 
  where
   doConfig :: MonadIO m => UserSettings -> m ()

docs/guide.md

@@ -97,6 +97,10 @@ This is the complete list of env variables that change GHCup behavior:
 * `GHCUP_SKIP_UPDATE_CHECK`: Skip the (possibly annoying) update check when you run a command
 * `CC`/`LD` etc.: full environment is passed to the build system when compiling GHC via GHCup
 
+On windows, there's additionally:
+
+* `GHCUP_MSYS2`: Has to point to the root of an existing MSYS2 installation (when installed by GHCup, that's e.g. `C:\ghcup\msys64`). GHCup bootstrap takes care of this usually.
+
 ### XDG support
 
 To enable XDG style directories, set the environment variable `GHCUP_USE_XDG_DIRS` to anything.
@@ -198,6 +202,50 @@ url-source:
   - "https://raw.githubusercontent.com/haskell/ghcup-metadata/master/ghcup-prereleases-0.0.7.yaml"
 ```
 
+## Stack integration
+
+Stack manages GHC versions internally by default. In order to make it use ghcup installed
+GHC versions there are two strategies.
+
+### Strategy 1: System GHC (works on all stack versions)
+
+You can instruct stack to use "system" GHC versions (whatever is in PATH). To do so,
+run the following commands:
+
+```sh
+stack config set install-ghc false --global
+stack config set system-ghc  true  --global
+```
+
+### Strategy 2: Stack hooks (new, recommended)
+
+Since stack 2.9.1 you can customize the installation logic of GHC completely, see [https://docs.haskellstack.org/en/stable/yaml_configuration/#ghc-installation-customisation](https://docs.haskellstack.org/en/stable/yaml_configuration/#ghc-installation-customisation).
+
+We can use this to simply invoke ghcup whenever stack is trying to install/discover a GHC versions. This
+is done via placing a shell script at `~/.stack/hooks/ghc-install.sh` and making it executable.
+
+The ghcup bootstrap script asks you during installation whether you want to install this shell script. You can also
+install/update it manually like so:
+
+```sh
+mkdir -p ~/.stack/hooks/
+curl https://raw.githubusercontent.com/haskell/ghcup-hs/master/scripts/hooks/stack/ghc-install.sh \
+  > ~/.stack/hooks/ghc-install.sh
+chmod +x ~/.stack/hooks/ghc-install.sh
+# hooks are only run when 'system-ghc: false'
+stack config set system-ghc false --global
+```
+
+By default, when the hook fails for whatever reason, stack will fall back to its own installation logic. To disable
+this, run `stack config set install-ghc false --global`.
+
+### Windows
+
+On windows, you may find the following config options useful too:
+`skip-msys`, `extra-path`, `extra-include-dirs`, `extra-lib-dirs`.
+
+Also check out: [https://docs.haskellstack.org/en/stable/yaml_configuration](https://docs.haskellstack.org/en/stable/yaml_configuration)
+
 # More on installation
 
 ## Customisation of the installation scripts