man: Document how to select subkeys with --gpg-sign

See the ‘HOW TO SPECIFY A USER ID’ section of `man 1 gpg`; or
https://stackoverflow.com/a/48240076/2931197.

This will be important when rotating signing subkeys for an OSTree
repository.

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

diff --git a/man/ostree-commit.xml b/man/ostree-commit.xml
index a5fd8d2869e2a6894342d12c9b6507cc467623dc..7de5b0f76eab64106607406f01a5ad0576f3f3ab 100644 (file)
--- a/man/ostree-commit.xml
+++ b/man/ostree-commit.xml
@@ -265,6 +265,10 @@ License along with this library. If not, see <https://www.gnu.org/licenses/>.
 
                 <listitem><para>
                     GPG Key ID with which to sign the commit (if built with GPGME - GNU Privacy Guard Made Easy).
+                </para>
+
+                <para>
+                    To use a specific subkey, pass the subkey’s fingerprint followed by <literal>!</literal>.
                 </para></listitem>
             </varlistentry>
 

diff --git a/man/ostree-summary.xml b/man/ostree-summary.xml
index 19e014ed6bf579419d95fbbb11d28830eef9a8f4..222c6b04ee955d8fbb3eb7d2da48b976f4b3b360 100644 (file)
--- a/man/ostree-summary.xml
+++ b/man/ostree-summary.xml
@@ -118,6 +118,10 @@ License along with this library. If not, see <https://www.gnu.org/licenses/>.
 
                 <listitem><para>
                     GPG Key ID to sign the summary with.
+                </para>
+
+                <para>
+                    To use a specific subkey, pass the subkey’s fingerprint followed by <literal>!</literal>.
                 </para></listitem>
             </varlistentry>