Ensuring support is compiled in
-------------------------------
Tin will compile in support for PGP if it can find it.

It looks for 'pgpk' on the path
If this is found, then PGP5 support is assumed
Otherwise it looks for 'pgp' on the path
If this is found, then PGP2 support is assumed
If neither is found, then no pgp support is compiled in
If configure is called with --disable-pgp, then no pgp support is compiled in

When you try to use PGP
-----------------------
PGP2 support expects pubring.pgp
PGP5    "      "     pubring.pkr

It wants to find the above in:
$HOME/.pgp/pubring.*

Or you can override this with $PGPPATH/pubring.*

If an environment var PGPOPTS is defined, then tin will use it.

Internal usage of PGP
---------------------
There are 3 places where pgp is invoked:

1) Checking articles (^G in the pager)

   If the article is pgp signed (-----BEGIN PGP SIGNED MESSAGE-----)

   PGP2:  pgp -f $PGPOPTS <article >/dev/null
   PGP5:  pgpv -f $PGPOPTS <article >/dev/null

   If the article has (-----BEGIN PGP PUBLIC KEY BLOCK-----)

   pgp $PGPOPTS -ka article
   pgpk $PGPOPTS -a article

2) When posting news or mail

   -at are always used

   PGP2:

   -e  appended for encrypt
   -s  appended for signing

   pgp $PGPOPTS options plaintextfile to_address

   If tinrc.mail_address is defined then

   pgp $PGPOPTS options plaintextfile to_address -u tinrc.mail_address

   PGP5:

   If encrypting _and_ signing, -s is appended to the basic -at options

   pgpe is used if encrypting and pgps in all other cases. The command line
   used is:

   pgp_command $PGPOPTS options plaintextfile to_address

3) Appending public key

   PGP2: pgp $PGPOPTS -kxa from_address keyfile
   PGP5: pgpk $PGPOPTS -xa from_address -o keyfile

   Where address is the posting/mailing address

This file is correct as of tin-1.4.0