added documentation for pacman listings (#19)

README.md

@@ -129,8 +129,23 @@ This is a little collection of useful regexes that can be used for filtering.
 
 Sometimes using `--exclude` is easier than trying to create an exclusion regex. 
 
+## Using pkghist's output as input for pacman
+You can use the result of a `pkghist` query as input for pacman.
+
+To create an output in the matching format, use the `--no-colors` and the `--no-details' options in your query. 
+
+The following command installs all packages that have been removed after 2019-10-01 12:00. 
+```bash
+sudo pacman -S $(pkghist --no-details --no-colors --removed-only --after "2019-10-01 12:00"')                                             
+```
+
+The following command removes all packages that have been installed after 2019-10-02 12:00. 
+```bash
+sudo pacman -R $(pkghist --no-details --no-colors --after "2019-10-02 12:00"')                                                            
+```
+
 ## Shell completions
 `pkghist` creates completion scripts for `bash`, `fish` and `zsh`.
-They are created at build time using the great [clap library](https://github.com/clap-rs/clap). 
+They are created at build time using the great [clap crate](https://github.com/clap-rs/clap). 
 When installing using `makepkg` (e.g. using the AUR), they are put into the appropriate location.
 When installing manually, you may copy them from [the completions directory](./completions) into the appropriate location.