New docs

docs/commands/global-options.md

@@ -1,2 +1,44 @@
 # Global options
 
+## `dcr --help`
+
+```sh
+dcr --help
+```
+
+Prints top-level CLI usage, commands, flags, and examples.
+
+## `dcr --version`
+
+```sh
+dcr --version
+```
+
+Prints:
+
+```text
+dcr <version> (<target>)
+```
+
+## `dcr --update`
+
+```sh
+dcr --update
+```
+
+Update flow:
+
+1. Requests latest release from GitHub API.
+2. Finds asset matching current `DCR_TARGET`.
+3. Downloads replacement binary.
+4. Replaces current executable via `self-replace`.
+
+Limitations and behavior:
+
+- No extra arguments are accepted.
+- Requires network access to GitHub API/assets.
+- On Linux, if binary is owned by pacman, DCR prints package-manager update instructions instead of self-updating.
+
+## Running without command
+
+Running plain `dcr` (without arguments) shows help output.