Add profile support to app configuration (#6)

* Rename the api_key field since the key may not, and probably won't, be a JWT.

* Replace 'config-rs' usage with our own custom config handling.

'config-rs' is handy, but we plan to restructure the configuration file in a way that does not align well with that project's design. Rather than fight it, we've opted to replace it.

* Break configuration loading up a bit to make testing easier.

* Split up the `config` module to make the code easier to follow.

* Make `ConfigFile` the primary entry point for loading configuration from YAML.

* Allow loading non-default profiles from the application config file.

* Add new CLI option for selecting the configuration profile to use.

* Make `config` responsible for providing default values.

* Split up code for loading settings from environment variables.

* Split up code for loading settings from config files.

Also change profile merging to be a functional operation since it makes testing easier and it's not on a hot enough path to worry about extra data copies.

* Add support for profile inheritance in the app config file.

This change also adds error handling for config file issues.

* Update config file template to work with profiles.

* Update docs for new config file format supporting multiple profiles.

Cargo.toml

@@ -31,18 +31,19 @@ clap = "2.33.3"
 [dependencies]
 clap = "2.33.3"
 color-eyre = "0.5"
-config = "0.10"
 directories = "3.0"
 edit = "0.1.2"
 graphql_client = "0.9.0"
 indoc = "1.0"
 once_cell = "1.4.1"
 reqwest = { version = "0.10.8", features = ["blocking", "json"] }
-serde = "1.0.116"
+serde = { version = "1.0", features = ["derive"] }
+serde_yaml = "0.8"
 termcolor = "1.1"
 
 [dev-dependencies]
 assert_cmd = "1.0"
+assert_matches = "1.4"
 predicates = "1.0"
 rusty-hook = "0.11.2"
 serial_test = "0.5.0"

README.md

@@ -30,9 +30,24 @@ The available configuration options are:
 
 ```yaml
 --- 
-api_key: <Your personal access token>
+profiles:
+  default:
+    api_key: <Your personal access token>
+
+  another_profile:
+    source_profile: default
+    api_key: <Another personal access token>
 ```
 
+Note that you can have multiple named profiles in your configuration, allowing you to maintain multiple sets of configuration fields in the configuration file.
+Values can be inherited from one profile to another by way of the `source_profile` configuration field.
+Profiles without an explicit `source_profile` configuration implicitly inherit from the _default_ profile.
+You may choose which profile to use by passing the `--profile` to the CloudTruth CLI binary:
+
+`cloudtruth --profile another-profile <subcommand>`
+
+If the `--profile` argument is not supplied, the profile named _default_ will be used.
+
 ### Environment-based Configuration
 
 The CloudTruth CLI utility maps all environment variables with the `CT_` followed by a configuration name to the same settings as would be available in the configuration file format.
@@ -72,12 +87,21 @@ To see the full list of supported shells, you can run:
 
 All subcommands support a `--help` option to show you how the command should be invoked.
 
+### Switching Active Configuration Profile
+
+CloudTruth CLI profiles are a way of organizing the application's configuration data into multiple named groups.
+Profiles, in this sense, are unrelated to configuration values in your CloudTruth account.
+They simply allow you to configure the CloudTruth CLI for multiple organizations or multiple API keys with different access restrictions.
+By default, the profile named _default_ will be used, but you can select the active profile with the `--profile` flag:
+
+`cloudtruth --profile my-profile parameters get my_param`
+
 ### Switching Active CloudTruth Environment
 
 By default, all commands will run against the _default_ CloudTruth environment.
 To change the target environment, you can supply the global `--env` flag:
 
-`cloudtruth --env=production parameters get my_param`
+`cloudtruth --env production parameters get my_param`
 
 
 Development

src/cli.rs

@@ -26,6 +26,14 @@ pub fn build_cli() -> App<'static, 'static> {
                 .help("The CloudTruth environment to work with")
                 .takes_value(true),
         )
+        .arg(
+            Arg::with_name("profile")
+                .short("p")
+                .long("profile")
+                .help("The profile from the application configuration file to use")
+                .takes_value(true)
+                .default_value("default")
+        )
         .subcommand(
             SubCommand::with_name("completions")
                 .about("Generate shell completions for this application")