git: dd926806a723 - stable/15 - build.7: Explain update-packages repo signing

The branch stable/15 has been updated by ziaee:

URL: https://cgit.FreeBSD.org/src/commit/?id=dd926806a723b99c9184ce44ab68b83c03fdc173

commit dd926806a723b99c9184ce44ab68b83c03fdc173
Author:     Alexander Ziaee <ziaee@FreeBSD.org>
AuthorDate: 2026-04-28 16:55:11 +0000
Commit:     Alexander Ziaee <ziaee@FreeBSD.org>
CommitDate: 2026-05-01 15:13:02 +0000

    build.7: Explain update-packages repo signing
    
    MFC after:              3 days
    Reported by:            kevans
    Reviewed by:            kevans, ngie
    Differential Revision:  https://reviews.freebsd.org/D56607
    
    (cherry picked from commit ab98fd3234304ea10db3dee70205828d372c443a)
---
 share/man/man7/build.7 | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/share/man/man7/build.7 b/share/man/man7/build.7
index 6d040b6f8f02..7947f6186b71 100644
--- a/share/man/man7/build.7
+++ b/share/man/man7/build.7
@@ -25,7 +25,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd April 22, 2026
+.Dd April 28, 2026
 .Dt BUILD 7
 .Os
 .Sh NAME
@@ -373,10 +373,18 @@ defaults to
 Create or update the
 .Xr freebsd-base 7
 package repository for the base system.
+.Bl -bullet
+.It
 If an old repository is being updated,
 then packages whose contents have not changed since the previous version
 will be copied into the new repository to avoid needless updating of the
 version number.
+.It
+If
+.Va PKG_REPO_SIGNING_KEY
+is defined, the repo will be signed according to
+.Xr pkg-repo 8 .
+.El
 .It Cm xdev-build
 Builds for the
 .Cm xdev
@@ -1152,6 +1160,7 @@ Study the examples above.
 .Xr config 8 ,
 .Xr etcupdate 8 ,
 .Xr nextboot 8 ,
+.Xr pkg-repo 8 ,
 .Xr shutdown 8
 .Sh HISTORY
 The