Shell commands (#547)

* Implement shell interaction commands

* Use slice instead of iterator for shell invocation

* Default to `sh` instead of `$SHELL` for shell commands

* Enforce trailing comma in `commands` macro

* Use `|` register for shell commands

* Move shell config to `editor` and use in command

* Update shell command prompts

* Remove clone of shell config

* Change shell function names to match prompts

* Log stderr contents upon external command error

* Remove `unwrap` calls on potential common errors

`shell` will no longer panic if:
  * The user-configured shell cannot be found
  * The shell command does not output UTF-8

* Remove redundant `pipe` parameter

* Rename `ShellBehavior::None` to `Ignore`

* Display error when shell command is used and `shell = []`

* Document shell commands in `keymap.md`

1 files changed, 5 insertions, 0 deletions

diff --git a/helix-term/src/keymap.rs b/helix-term/src/keymap.rs
index 492dc292..f3e160b1 100644
--- a/helix-term/src/keymap.rs
+++ b/helix-term/src/keymap.rs
@@ -508,6 +508,11 @@ impl Default for Keymaps {
             },
 
             "\"" => select_register,
+            "|" => shell_pipe,
+            "A-|" => shell_pipe_to,
+            "!" => shell_insert_output,
+            "A-!" => shell_append_output,
+            "$" => shell_keep_pipe,
             "C-z" => suspend,
         });
         let mut select = normal.clone();