Update README

README.md

@@ -1,22 +1,14 @@
 # xcode-simulator-cert
 
-[![Swift 5 compatible][swift-badge]][Swift] [![Xcode 10.2 compatible][xcode-badge]][Xcode] 
+[![Swift 5 compatible][swift-badge]][Swift] [![Xcode 10.2 compatible][xcode-badge]][Xcode] [![Xcode 10.2 compatible][xcode-beta-badge]][Xcode] 
 
-This is a tool to manage [root certificates][RootCertificate] in Xcode simulators. 
+This is a tool to manage [root certificates][RootCertificate] in Xcode simulators.  Installing a certificate in all your simulators is as easy as:
-
-If you have a certificate for your server in PEM format in a file `myhost.crt`, type:
 
 ```bash
 $ xcode-simulator-cert install myhost.crt
 ```
 
-It will then install the certificate in all your simulators. You can also specify a specific simulator:
+It will then install the certificate in all your simulators. 
-
-```bash
-$ xcode-simulator-cert install myhost.crt --device-name="iPhone 8"
-```
-
-There are also some other subcommands and options available. `--help` is your friend.
 
 ## Installation
 
@@ -36,13 +28,57 @@ $ brew install skagedal/formulae/xcode-simulator-cert
 $ mint install skagedal/xcode-simulator-cert
 ```
 
+## Usage
+
+`xcode-simulator-tool` basically does CRUD actions for certificates in simulators: install new ones, export existing ones, remove certificates, and list them. 
+
+Use `xcode-simulator-tool --help` to get a quick overview of how it works.
+
+### Installing certificates
+
+The `install` subcomand takes a parameter where you give the certificate in PEM format. 
+
+```bash
+$ xcode-simulator-cert install myhost.crt
+```
+
+You can also specify a specific simulator:
+
+```bash
+$ xcode-simulator-cert install myhost.crt --device-name="iPhone 8"
+```
+
+This will install the certificate in simulators whose name exactly matches "iPhone 8". There are some other ways of filtering into which simulators to affect, please see `xcode-simulator-cert install --help`. 
+
+It will skip installing in simulators where this exact certificate already exist. 
+
+### Exporting certificates
+
+The `export` subcommand exports existing root certificate that it finds in the trust store of selected devices, creating a PEM file for each unique certificate.
+
+```
+$ xcode-simulator-cert export 
+```
+
+### Removing certificates
+
+The `remove` subcommand removes all root certificates from selected devices. 
+
+### List certificates
+
+The `list` subcommand lists all simulator devices and what certificates are available for each.
+
+## Caveats
+
+This tool edits a SQLite database managed by iOS in the simulator.  It is not using officially blessed APIs.  I have tested it on Xcode 10.2.1 and the Xcode 11 beta 1 (at the time of writing, the latest) and it works well, but I can of course not give any guarantees.  In some situations you may still need to manually go in and trust the certificate manually. I recommend not running the Xcode simulator while you run the tool.  
+
 ## Development
 
 If you'd like to hack on `xcode-simulator-cert`, you may run `generate-xcodeproj.sh` to generate an Xcode project. 
 
 ## Acknowledgements
 
-This tool is largely based on the work of Daniel Cerutti and his [ADVTrustStore] tool.  `xcode-simulator-cert` doesn't do much more than what his tool does at the moment.  I mostly just wanted to rewrite it in Swift.
+This tool is largely based on the work of Daniel Cerutti and his [ADVTrustStore] tool and documentation.  
 
 [ADVTrustStore]: https://github.com/ADVTOOLS/ADVTrustStore
 [Homebrew]: https://brew.sh
@@ -53,3 +89,4 @@ This tool is largely based on the work of Daniel Cerutti and his [ADVTrustStore]
 
 [swift-badge]: https://img.shields.io/badge/swift-5-orange.svg?style=flat
 [xcode-badge]: https://img.shields.io/badge/xcode-10.2-blue.svg?style=flat 
+[xcode-beta-badge]: https://img.shields.io/badge/xcode-11_beta1-blue.svg?style=flat