doc: clarify -e -i docs

Fixes FiloSottile#339

doc/age.1.ronn

@@ -47,7 +47,7 @@ overhead per recipient, plus 16 bytes every 64KiB of plaintext.
  Encrypt to the explicitly specified <RECIPIENT>. See the
  [RECIPIENTS AND IDENTITIES][] section for possible recipient formats.
 
- This option can be repeated and combined with `-R`/`--recipients-file`,
+ This option can be repeated and combined with other recipient flags,
  and the file can be decrypted by all provided recipients independently.
 
 * `-R`, `--recipients-file`=<PATH>:
@@ -58,15 +58,14 @@ overhead per recipient, plus 16 bytes every 64KiB of plaintext.
  If <PATH> is `-`, the recipients are read from standard input. In
  this case, the <INPUT> argument must be specified.
 
- This option can be repeated and combined with `-r`/`--recipient`,
+ This option can be repeated and combined with other recipient flags,
  and the file can be decrypted by all provided recipients independently.
 
 * `-p`, `--passphrase`:
  Encrypt with a passphrase, requested interactively from the terminal.
  `age` will offer to auto-generate a secure passphrase.
 
- This option can't be used with `-r`/`--recipient` or
- `-R`/`--recipients-file`.
+ This option can't be used with other recipient flags.
 
 * `-a`, `--armor`:
  Encrypt to an ASCII-only "armored" encoding.
@@ -77,6 +76,27 @@ overhead per recipient, plus 16 bytes every 64KiB of plaintext.
 
  Decryption transparently detects and decodes ASCII armoring.
 
+* `-i`, `--identity`=<PATH>:
+ Encrypt to the [RECIPIENTS][RECIPIENTS AND IDENTITIES] corresponding to the
+ [IDENTITIES][RECIPIENTS AND IDENTITIES] listed in the file at <PATH>. This
+ is equivalent to converting the file at <PATH> to a recipients file with
+ `age-keygen -y` and then passing that to `-R`/`--recipients-file`.
+
+ For the format of <PATH>, see the definition of `-i`/`--identity` in the
+ [Decryption options][] section.
+
+ `-e`/`--encrypt` must be explicitly specified when using `-i`/`--identity`
+ in encryption mode to avoid confusion.
+
+* `-j` <PLUGIN>:
+ Encrypt using the data-less [plugin][Plugins] <PLUGIN>.
+
+ This is equivalent to using `-i`/`--identity` with a file that contains a
+ single plugin `IDENTITY` that encodes no plugin-specific data.
+
+ `-e`/`--encrypt` must be explicitly specified when using `-j` in encryption
+ mode to avoid confusion.
+
 ### Decryption options
 
 * `-d`, `--decrypt`:
@@ -116,20 +136,12 @@ overhead per recipient, plus 16 bytes every 64KiB of plaintext.
  Unused identities are ignored, but it is an error if the <INPUT> file is
  passphrase-encrypted and `-i`/`--identity` is specified.
 
- If `-e`/`--encrypt` is explicitly specified (to avoid confusion),
- `-i`/`--identity` may also be used to encrypt to the `RECIPIENTS`
- corresponding to the `IDENTITIES` listed at <PATH>. This allows using an
- identity file as a symmetric key, if desired.
-
 * `-j` <PLUGIN>:
  Decrypt using the data-less [plugin][Plugins] <PLUGIN>.
 
  This is equivalent to using `-i`/`--identity` with a file that contains a
  single plugin `IDENTITY` that encodes no plugin-specific data.
 
- If `-e`/`--encrypt` is explicitly specified (to avoid confusion), `-j` may
- also be used to encrypt with a data-less plugin.
-
 ## RECIPIENTS AND IDENTITIES
 
 `RECIPIENTS` are public values, like a public key, that a file can be encrypted