portage(5): fix description of volatile attribute

The description of the 'volatile' keyword in the 'repos.conf' section in the portage(5)
man page seems to be inconsistent.

I think the first two sentences correctly describe the behaviour of 'volatile' and
agree with the comments in portage/repository/config.py:
"Specifies whether a repository is volatile.  Volatile repositories are assumed to
contain changes made outside of Portage.  This prohibits optimizations from occurring
by assuming the integrity of the repository and its caches may be  violated."

The remainder of the paragraph inverts the meaning of 'volatile' and does not
agree with the code in portage/repository/config.py:
"Disabling this option allows local changes to be made to the repository for
e.g. development safely.  For git-synced repositories, Portage will not perform
destructive operations.  Per default, repositories are considered volatile if
their directory is owned by either 'root' or 'portage' and if it is under
/var/db/repos. Otherwise, the repository is considered non volatile."

Bug: https://bugs.gentoo.org/911594
Signed-off-by: Christian Becke <[email protected]>
Signed-off-by: Sam James <[email protected]>

man/portage.5

@@ -1265,11 +1265,11 @@ sync\-openpgp\-key\-path setting. Defaults to no, false.
 Specifies whether a repository is volatile.  Volatile repositories
 are assumed to contain changes made outside of Portage.  This prohibits
 optimizations from occurring by assuming the integrity of the repository
-and its caches may be violated.  Disabling this option allows local changes to
-be made to the repository for e.g. development safely.  For git-synced
-repositories, Portage will not perform destructive operations.
-Per default, repositories are considered volatile if their directory is owned
-by either 'root' or 'portage' and if it is under /var/db/repos. Otherwise,
+and its caches may be violated.  Enabling this option allows local changes to
+be made to the repository for e.g. development safely.  When enabled, Portage
+will not perform destructive operations for git-synced repositories.  Per
+default, repositories are considered volatile if their directory is not owned
+by either 'root' or 'portage' or if it is not under /var/db/repos.  Otherwise,
 the repository is considered non volatile.
 .TP