enable generic env variables

docs/markdown/backend/available.md

@@ -4,6 +4,8 @@ In theory [all the restic backends](https://restic.readthedocs.io/en/stable/030_
 
 Those tested are the following:
 
+> ℹ️ You can also [specify the `env` variables in a config file](/backend/env) to separate them from the config file.
+
 ## Local
 
 ```yaml

docs/markdown/backend/env.md

@@ -1,36 +1,67 @@
 # Environment
 
-> ⚠ Available since version `v1.3.0`
+> ⚠ Available since version `v1.4.0`
 
 Sometimes it's favorable not having the encryption keys in the config files.
-For that `autorestic` allows passing the backend keys as `ENV` variables, or through an env file.
+For that `autorestic` allows passing the env variables to backend password as `ENV` variables, or through an env file.
+You can also pass whatever `env` variable to restic by prefixing it with `AUTORESTIC_[BACKEND NAME]_`.
 
-The syntax for the `ENV` variables is as follows: `AUTORESTIC_[BACKEND NAME]_KEY`.
+> ℹ️ Env variables and file overwrite the config file in the following order:
+>
+> Env Variables > Env File (`.autorestic.env`) > Config file (`.autorestic.yaml`)
+
+## Env file
+
+Alternatively `autorestic` can load an env file, located next to `.autorestic.yml` called `.autorestic.env`.
+
+```
+AUTORESTIC_FOO_RESTIC_PASSWORD=secret123
+```
+
+### Example with repository password
+
+The syntax for the `ENV` variables is as follows: `AUTORESTIC_[BACKEND NAME]_RESTIC_PASSWORD`.
 
 ```yaml | autorestic.yaml
 backend:
   foo:
     type: ...
     path: ...
-    key: secret123 # => AUTORESTIC_FOO_KEY=secret123
+    key: secret123 # => AUTORESTIC_FOO_RESTIC_PASSWORD=secret123
 ```
 
-## Example
-
 This means we could remove `key: secret123` from `.autorestic.yaml` and execute as follows:
 
 ```bash
-AUTORESTIC_FOO_KEY=secret123 autorestic backup ...
+AUTORESTIC_FOO_RESTIC_PASSWORD=secret123 autorestic backup ...
 ```
 
-## Env file
+### Example with Backblaze B2
+
+```yaml | autorestic.yaml
+backends:
+  bb:
+    type: b2
+    path: myBucket
+    key: myPassword
+    env:
+      B2_ACCOUNT_ID: 123
+      B2_ACCOUNT_KEY: 456
+```
 
-Alternatively `autorestic` can load an env file, located next to `autorestic.yml` called `.autorestic.env`.
+You could create an `.autorestic.env` or pass the following `ENV` variables to autorestic:
 
-```| .autorestic.env
-AUTORESTIC_FOO_KEY=secret123
+```
+AUTORESTIC_BB_RESTIC_PASSWORD=myPassword
+AUTORESTIC_BB_B2_ACCOUNT_ID=123
+AUTORESTIC_BB_B2_ACCOUNT_KEY=456
 ```
 
-after that you can simply use `autorestic` as your are used to.
+```yaml | autorestic.yaml
+backends:
+  bb:
+    type: b2
+    path: myBucket
+```
 
 > :ToCPrevNext

internal/backend.go

@@ -58,20 +58,27 @@ func (b Backend) generateRepo() (string, error) {
 
 func (b Backend) getEnv() (map[string]string, error) {
 	env := make(map[string]string)
+	// Key
 	if b.Key != "" {
 		env["RESTIC_PASSWORD"] = b.Key
-	} else {
-		key, err := b.getKey()
-		if err != nil {
-			return nil, err
-		}
-		env["RESTIC_PASSWORD"] = key
 	}
+
+	// From config file
 	repo, err := b.generateRepo()
 	env["RESTIC_REPOSITORY"] = repo
 	for key, value := range b.Env {
 		env[strings.ToUpper(key)] = value
 	}
+
+	// From Envfile and passed as env
+	var prefix = "AUTORESTIC_" + strings.ToUpper(b.name) + "_"
+	for _, variable := range os.Environ() {
+		var splitted = strings.SplitN(variable, "=", 2)
+		if strings.HasPrefix(splitted[0], prefix) {
+			env[strings.TrimPrefix(splitted[0], prefix)] = splitted[1]
+		}
+	}
+
 	return env, err
 }
 
@@ -85,17 +92,6 @@ func generateRandomKey() string {
 	return key
 }
 
-func (b Backend) getKey() (string, error) {
-	if b.Key != "" {
-		return b.Key, nil
-	}
-	keyName := "AUTORESTIC_" + strings.ToUpper(b.name) + "_KEY"
-	if key, found := os.LookupEnv(keyName); found {
-		return key, nil
-	}
-	return "", fmt.Errorf("no key found for backend \"%s\"", b.name)
-}
-
 func (b Backend) validate() error {
 	if b.Type == "" {
 		return fmt.Errorf(`Backend "%s" has no "type"`, b.name)
@@ -105,8 +101,9 @@ func (b Backend) validate() error {
 	}
 	if b.Key == "" {
 		// Check if key is set in environment
-		if _, err := b.getKey(); err != nil {
-			// If not generate a new one
+		env, _ := b.getEnv()
+		if _, found := env["RESTIC_PASSWORD"]; !found {
+			// No key set in config file or env => generate random key and save file
 			key := generateRandomKey()
 			b.Key = key
 			c := GetConfig()