docs: correct -log level options and document env vars

The -log flag is parsed by logrus.ParseLevel which accepts level names,
not the numeric scale the help text and README advertised. Also add an
Environment Variables section documenting MASTERPW and the ENP_PIN_*
inputs, which were only discoverable from the source.

Author: hazcod

README.md

@@ -65,7 +65,7 @@ Flags
 | `-vault=PATH` | Path to your Enpass vault |
 | `-keyfile=PATH` | Path to your Enpass vault keyfile |
 | `-type=TYPE` | The type of your card (password, ...) |
-| `-log=LEVEL` | The log level from debug (5) to error (1) |
+| `-log=LEVEL` | The log level (trace, debug, info, warn, error, fatal, panic) |
 | `-nonInteractive` | Disable prompts and fail instead |
 | `-json` | Output as JSON to stdout |
 | `-pin` | Enable Quick Unlock using a PIN |
@@ -81,6 +81,15 @@ Flags
 | `-category=CATEGORY` | Category for `create`/`edit` commands (default: Login) |
 | `-force` | Skip confirmation prompts for `trash`/`delete` commands |
 
+Environment Variables
+-----
+| Name | Description |
+| :---: | --- |
+| `MASTERPW` | Vault master password (skips the interactive prompt) |
+| `ENP_PIN` | PIN value when `-pin` is enabled (skips the PIN prompt) |
+| `ENP_PIN_PEPPER` | Pepper mixed into the PIN-derived key |
+| `ENP_PIN_ITER_COUNT` | KDF iteration count for the PIN (default: 100000) |
+
 Development
 -----
 ```shell

cmd/enpasscli/main.go

@@ -84,7 +84,7 @@ func (args *Args) parse() {
 	args.vaultPath = flag.String("vault", "", "Path to your Enpass vault.")
 	args.cardType = flag.String("type", "password", "The type of your card. (password, ...)")
 	args.keyFilePath = flag.String("keyfile", "", "Path to your Enpass vault keyfile.")
-	args.logLevelStr = flag.String("log", defaultLogLevel.String(), "The log level from debug (5) to error (1).")
+	args.logLevelStr = flag.String("log", defaultLogLevel.String(), "The log level: trace, debug, info, warn, error, fatal, panic.")
 	args.jsonOutput = flag.Bool("json", false, "Output data in JSON format.")
 	args.nonInteractive = flag.Bool("nonInteractive", false, "Disable prompts and fail instead.")
 	args.pinEnable = flag.Bool("pin", false, "Enable PIN.")