Implement and document the NICE config option

Thanks to Joni Martikainen for the suggestion.

(While editing the NEWS file, I also moved the -r item to FEATURES
since, while legal, -r combos weren't useful and now they are, so I
guess it's more a featureling than a modification.)

src/etc/sbopkg/sbopkg.conf

@@ -30,6 +30,7 @@ CLEANUP=${CLEANUP:-NO}
 DEBUG_UPDATES=${DEBUG_UPDATES:-0}
 KEEPLOG=${KEEPLOG:-YES}
 MKDIR_PROMPT=${MKDIR_PROMPT:-YES}
+NICE=${NICE:-10}
 REPO_BRANCH=${REPO_BRANCH:-13.37}
 REPO_NAME=${REPO_NAME:-SBo}
 

src/usr/doc/NEWS

@@ -10,6 +10,15 @@ sbopkg xxxVERSIONxxx (xxxDATExxx)
           the feature request and some testing and to Mauro Giachero for
           the initial patch and discussion and review of additional
           patching.
+        * It is now possible to combine the -r flag with other flags
+          such that a sync is performed first. For example 'sbopkg -ri
+          foo' will synchronize with the repo and install the latest
+          foo.
+        * There is a new configuration option, NICE, which enables the
+          user to specify a niceness for the execution of the
+          SlackBuild. Previously, this was hardcoded to 10 (which is
+          still the default). Thanks to Joni Martikainen for the
+          suggestion.
 
     MODIFICATIONS
 
@@ -19,10 +28,6 @@ sbopkg xxxVERSIONxxx (xxxDATExxx)
         * The 'Build' option in a package's info menu has been renamed
           to 'Process', along with many other minor informational
           changes throughout the UI.
-        * It is now possible to combine the -r flag with other flags
-          such that a sync is performed first. For example 'sbopkg -ri
-          foo' will synchronize with the repo and install the latest
-          foo.
 
 sbopkg 0.35.0 (2011-04-28 02:48 UTC)
 

src/usr/doc/THANKS

@@ -78,3 +78,4 @@ Thank you!
  875 dmotaleite (suggestion)
  894 Sergey V. (bash completion)
  905 Kristoffer Karlsson (suggestion)
+ 911 Joni Martikainen (suggestion)

src/usr/man/man5/sbopkg.conf.5

@@ -222,6 +222,36 @@ The default assignment is:
 \fCxxxMKDIR_PROMPTxxx\fP
 .\"---------------------------------------------------------------------
 .TP
+.B NICE
+Integer.
+.IP
+This value is passed to
+.BR nice (1)
+as its
+.B \-n
+argument.
+.\" I had to 'hardcode' the default here to explain things so, while the
+.\" 'The default assignment is' will be automatically updated, remember
+.\" to also change this text if we ever set the niceness to something
+.\" other than nice's default. (Not that we will.)
+If this value is unset or left at the default,
+.B sbopkg
+will execute SlackBuilds with
+.BR nice 's
+default niceness, which is
+.B 10.
+If you do not wish the priority to be effected, be sure to set it to
+.BR 0 .
+Note that this only affects SlackBuild execution and does not affect the
+priority of
+.B sbopkg
+as a whole.
+.IP
+The default assignment is:
+.IP
+\fCxxxNICExxx\fP
+.\"---------------------------------------------------------------------
+.TP
 .B OUTPUT
 Path.
 .IP
@@ -576,6 +606,7 @@ slakmagik
 .SH SEE ALSO
 .BR diff (1),
 .BR mktemp (1),
+.BR nice (1),
 .BR rsync (1),
 .BR sbopkg (8),
 .BR uname (1),

src/usr/sbin/sbopkg

@@ -3454,10 +3454,10 @@ build_package() {
             # deleting too much or leaving garbage behind us), a nice
             # approach is to use sbopkg's own temp directory.
             export TMP=$SBOPKGTMP
-            nice sh $PKGNAME.SlackBuild.build
+            nice -n ${NICE:-10} sh $PKGNAME.SlackBuild.build
             echo "Cleaning up..."
         else
-            nice sh $PKGNAME.SlackBuild.build
+            nice -n ${NICE:-10} sh $PKGNAME.SlackBuild.build
         fi
     )
 }