diff -r c486df8ea68a -r b68b8615c512 lib/update.updates
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/update.updates	Tue Mar 20 14:12:11 2012 +0200
@@ -0,0 +1,163 @@
+# vim: set ft=sh :
+#
+# Dependency-based updates + utils
+
+## Compare the given output file with all given source files:
+#
+#   check_update $out ${deps[@]} && do_update $out ... || ...
+#
+# Returns true if the output file needs to be updated.
+function check_update {
+    # target
+    local out=$1; shift
+
+    debug "$out"
+
+    # need update?
+    local update=
+
+    if [ ${#@} == 0 ]; then
+        debug "  update: unknown deps"
+        update=y
+
+    elif [ ! -e $out ]; then
+        debug "  update: dest missing"
+        update=y
+        
+    elif [ $UPDATE_FORCE ]; then
+        debug "  update: forced"
+        update=y
+    fi
+
+    # check deps
+    for dep in "$@"; do
+        # don't bother checking if already figured out
+        [ $update ] && continue
+
+        # check
+        if [ ! -e $ROOT/$dep ]; then
+            fail "$dst: Missing source: $dep"
+
+        elif [ $ROOT/$out -ot $ROOT/$dep ]; then
+            debug "  update: $dep"
+            update=y
+        else
+            debug "  check: $dep"
+        fi
+    done
+
+    [ ! $update ] && debug "  up-to-date"
+
+    # return
+    [ $update ]
+}
+
+## Generate updated output file from given command's stdout:
+#
+#   do_update $out $BIN/cmd --args
+#
+# Writes output to a temporary .new file, optionally shows a diff of changes, and commits
+# the new version to $out (unless noop'd).
+function do_update {
+    local out=$1; shift
+    local tmp=$out.new
+
+    debug "$out"
+    cmd "$@" > $ROOT/$tmp
+
+    # compare
+    if [ -e $ROOT/$out ] && [ $UPDATE_DIFF ]; then
+        debug "  changes:"
+
+        # terse
+        indent "        " diff --unified=1 $ROOT/$out $ROOT/$tmp || true
+    fi
+    
+    # deploy
+    if [ $UPDATE_NOOP ]; then
+        # cleanup
+        debug "  no-op"
+
+        cmd rm $ROOT/$tmp
+    else
+        # commit
+        debug "  deploy"
+
+        cmd mv $ROOT/$tmp $ROOT/$out
+    fi
+}
+
+## Look for a link target:
+#
+#   find_link   $lnk    $tgt...
+#
+# Outputs the first given target to exist, skipping any that are the same as the given $lnk.
+# If no $tgt matches, outputs the last one, or '-'.
+function choose_link {
+    local lnk=$1; shift
+    local tgt=-
+
+    for tgt in "$@"; do
+        [ $tgt != $out ] && [ -e $ROOT/$tgt ] && break
+    done
+    
+    echo $tgt
+}
+
+
+## Compare symlink to target:
+#
+#   check_link $lnk $tgt && do_link $lnk $tgt || ...
+#
+# Tests if the symlink exists, and the target matches.
+# Fails if the target does not exist.
+function check_link {
+    local lnk=$1
+    local tgt=$2
+
+    [ ! -e $ROOT/$tgt ] && fail "$tgt: target does not exist"
+    
+    [ ! -e $ROOT/$lnk ] || [ $(readlink $ROOT/$lnk) != $ROOT/$tgt ]
+}
+
+## Update symlink to point to target:
+#
+#   do_link $lnk $tgt
+#
+function do_link {
+    local lnk=$1
+    local tgt=$2
+
+    cmd ln -sf $ROOT/$tgt $ROOT/$lnk
+}
+
+## Update .serial number:
+#
+#   do_update_serial $serial
+#
+# Shows old/new serial on debug.
+function do_update_serial {
+    local serial=$1
+
+    # read
+    local old=$(test -e $ROOT/$serial && cat $ROOT/$serial || echo '')
+
+
+    cmd $BIN/update-serial $ROOT/$serial
+    
+    # read
+    local new=$(cat $ROOT/$serial)
+        
+    debug "  $old -> $new"
+}
+
+## Perform `hg commit` for $DATA
+function do_commit {
+    local msg=$1
+
+    indent "    " hg_diff
+
+    hg_commit "$msg"
+}
+
+