shell: specify an interactive shell using "garden.interactive-shell"

Allow the interactive shell to be configured separately via the
"garden.interactive-shell" configuration value. This allows custom commands
to be configured in "garden.shell" that take command strings while
specifying an interactive shell command via "garden.interactive-shell".

doc/src/changelog.md

@@ -29,6 +29,27 @@
   `garden <cmd> -z | --no-wordsplit` option to opt-out of this behavior.
   ([#25](https://github.com/davvid/garden/pull/25))
 
+- `garden.shell` can now be configured to use arbitrary commands for executing
+  command strings. Garden uses the configured `garden.shell` as-is and does
+  not augment its options (e.g. `-e`  or `-o shwordsplit`) when a custom command
+  is used. Custom commands are identified as commands that expand to 2 or more
+  command-line arguments. Thus, `python3` is not considered a custom command
+  and `garden` will run `python3 -c <string>` to run commands. On the other
+  hand, specifying `ruby -e` *is* considered a custom command because it
+  expands to `["ruby", "-e"]` under the hood. If you need to use a custom
+  command  that takes no additional command-line arguments then you can
+  use `env` as an extra argument to have it be considered as a custom shell.
+  For example, `env custom-shell` will cause `garden` to run
+  `env custom-shell <string>`, which is equivalent to `custom-shell <string>`.
+  Using just `custom-shell` would have resulted in `garden` running
+  `custom-shell -c <string>` instead, which may not be desired.
+  ([#26](https://github.com/davvid/garden/pull/26))
+
+- The `garden shell` command can now be configured to use an interactive command shell
+  that is distinct from the command specified in the `garden.shell` configuration by
+  configuring the `garden.interactive-shell` value.
+  ([#26](https://github.com/davvid/garden/pull/26))
+
 
 ## v1.2.1
 

doc/src/commands.md

@@ -698,6 +698,24 @@ The optional tree argument is not needed for the case where a garden
 and tree share a name -- garden will chdir into that same-named tree when
 creating the shell.
 
+If you would like to customize the command to use for `garden shell` then
+you can configure `garden.interactive-shell`. This value overrides `garden.shell`
+and is only used by the `garden shell` command.
+
+```yaml
+# Launch a fish login shell for "garden shell".
+garden:
+  interactive-shell: fish
+```
+
+Arbitrary command interpreters can be specified.
+
+```yaml
+# Launch a python interpreter for "garden shell".
+garden:
+  interactive-shell: python3 -B
+```
+
 
 ## garden ls
 

src/cmds/shell.rs

@@ -55,12 +55,16 @@ pub fn main(app_context: &model::ApplicationContext, options: &ShellOptions) ->
 
     // Evaluate garden.shell
     let graft_config = context.config.map(|id| app_context.get_config(id));
-    let shell_expr = config.shell.clone();
+    let shell_expr = if config.interactive_shell.is_empty() {
+        &config.shell
+    } else {
+        &config.interactive_shell
+    };
     let shell = eval::tree_value(
         app_context,
         config,
         graft_config,
-        &shell_expr,
+        shell_expr,
         &context.tree,
         context.garden.as_ref(),
     );

src/config/reader.rs

@@ -64,6 +64,19 @@ fn parse_recursive(
     if get_str(&doc[constants::GARDEN][constants::SHELL], &mut config.shell) && config_verbose > 0 {
         debug!("config: {} = {}", constants::GARDEN_SHELL, config.shell);
     }
+    // garden.interactive-shell
+    if get_str(
+        &doc[constants::GARDEN][constants::INTERACTIVE_SHELL],
+        &mut config.interactive_shell,
+    ) && config_verbose > 0
+    {
+        debug!(
+            "config: {} = {}",
+            constants::GARDEN_INTERACTIVE_SHELL,
+            config.interactive_shell
+        );
+    }
+
     // garden.shell-errexit
     if get_bool(
         &doc[constants::GARDEN][constants::SHELL_ERREXIT],

src/constants.rs

@@ -75,6 +75,7 @@ pub const GARDEN_CONFIG_DIR_EXPR: &str = "${GARDEN_CONFIG_DIR}";
 pub const GARDEN_ROOT: &str = "GARDEN_ROOT";
 
 /// Command-line defines for overriding configurable behavior.
+pub(crate) const GARDEN_INTERACTIVE_SHELL: &str = "garden.interactive-shell";
 pub(crate) const GARDEN_SHELL: &str = "garden.shell";
 pub(crate) const GARDEN_SHELL_ERREXIT: &str = "garden.shell-errexit";
 pub(crate) const GARDEN_SHELL_WORDSPLIT: &str = "garden.shell-wordsplit";
@@ -95,6 +96,10 @@ pub const GROUPS: &str = "groups";
 /// files directly into the configuration.
 pub const INCLUDES: &str = "includes";
 
+/// The "interactive-shell" key in the garden block overrides the
+/// command used by interactive "garden shell" sessions.
+pub const INTERACTIVE_SHELL: &str = "interactive-shell";
+
 /// The "links" key in a tree block defines URLs displayed by "garden ls".
 pub const LINKS: &str = "links";
 

src/model.rs

@@ -494,6 +494,7 @@ pub struct Configuration {
     pub root_is_dynamic: bool,
     pub root_path: std::path::PathBuf,
     pub shell: String,
+    pub interactive_shell: String,
     pub templates: HashMap<String, Template>,
     pub tree_search_path: Vec<std::path::PathBuf>,
     pub trees: IndexMap<TreeName, Tree>,
@@ -670,6 +671,9 @@ impl Configuration {
             }
             // Allow overridding garden.<value> using "garden -D garden.<value>=false".
             match name.as_str() {
+                constants::GARDEN_INTERACTIVE_SHELL => {
+                    self.interactive_shell = expr;
+                }
                 constants::GARDEN_SHELL => {
                     self.shell = expr;
                 }

tests/data/shell/custom.yaml

@@ -1,5 +1,6 @@
 garden:
   shell: zsh -c
+  interactive-shell: zsh
 
 commands:
   shell-words: |