environ: document GIT_SSL_NO_VERIFY

Even though the name of the environment variable is mentioned in
"git config --help" from http.sslVerify, there is no description for
it.  Add one.

Note that this is not a usual Boolean environment variable whose
value can be yes/true/on vs no/false/off; the existence of it is
enough to trigger the feature named by the variable.

Signed-off-by: Junio C Hamano <[email protected]>

Author: gitster

Documentation/git.txt

@@ -665,6 +665,11 @@ for further details.
 	plink or tortoiseplink. This variable overrides the config setting
 	`ssh.variant` that serves the same purpose.
 
+`GIT_SSL_NO_VERIFY`::
+	Setting and exporting this environment variable to any value
+	tells Git not to verify the SSL certificate when fetching or
+	pushing over HTTPS.
+
 `GIT_ASKPASS`::
 	If this environment variable is set, then Git commands which need to
 	acquire passwords or passphrases (e.g. for HTTP or IMAP authentication)