docs: add info on custom commands (aka saved prompts)

Author: meowgorithm

COMMANDS.md

@@ -0,0 +1,82 @@
+# Custom Commands in Crush
+
+Crush supports custom commands (sometimes called saved prompts) that can be
+created by users to quickly send predefined prompts to the AI assistant.
+
+## Creating Custom Commands
+
+Custom commands are predefined prompts stored as Markdown files in one of three
+locations:
+
+1. User Commands:
+
+   ```bash
+   # Unix-like systems (Linux, macOS, FreeBSD, etc.)
+   $XDG_CONFIG_HOME/crush/commands/
+
+   # Windows
+   %USERPROFILE%\AppData\Local\crush\commands\
+   ```
+
+2. Project Commands:
+
+   ```bash
+   <PROJECT DIR>/.crush/commands/
+   ```
+
+Each Markdown file in these directories becomes a custom command. The file name
+(without the extension) becomes the name of the command.
+
+For example, creating a file at `~/.config/crush/commands/carrot-cake.md` with
+the following content:
+
+```markdown
+RUN git ls-files
+READ README.md
+```
+
+...creates a command called `user:carrot-cake`.
+
+### Command Arguments
+
+Crush supports named arguments in custom commands using placeholders in the
+format `$NAME` (where NAME consists of uppercase letters, numbers, and
+underscores, and must start with a letter).
+
+For example:
+
+```markdown
+# Fetch Context for Issue $ISSUE_NUMBER
+
+RUN gh issue view $ISSUE_NUMBER --json title,body,comments
+RUN git grep --author="$AUTHOR_NAME" -n .
+RUN grep -R "$SEARCH_PATTERN" $DIRECTORY
+```
+
+When you run a command with arguments, crush will prompt you to enter values
+for each unique placeholder.
+
+### Organizing Commands
+
+Commands can be organized into sub-directories:
+
+```
+~/.config/crush/commands/git/commit.md
+```
+
+This creates a command with ID `user:git:commit`.
+
+### Using Custom Commands
+
+1. Press <kbd>Ctrl+p</kbd> to open the command dialog
+2. Press <kbd>Tab</kbd> to switch to User Commands
+3. Select your custom command
+
+---
+
+Part of [Charm](https://charm.land).
+
+<a href="https://charm.land/"><img alt="The Charm logo" width="400" src="https://stuff.charm.sh/charm-banner-next.jpg" /></a>
+
+<!--prettier-ignore-->
+Charm热爱开源 • Charm loves open source

README.md

@@ -449,6 +449,11 @@ To add specific models to the configuration, configure as such:
 }
 ```
 
+## Custom Commands (a.k.a. Saved Prompts)
+
+Crush has first-class support for this. See [COMMANDS.md](COMMANDS.md) for more
+information.
+
 ## Logging
 
 Sometimes you need to look at logs. Luckily, Crush logs all sorts of