ignore file update support

* etckeeper update-ignore will automatically update the VCS ignore
  file, only touching the part inside a "managed by etckeeper"
  comment block.
* Run etckeeper update-ignore on upgrade.

7 files changed, 169 insertions, 102 deletions

diff --git a/README b/README
index 248e2d5..6893f33 100644
--- a/README
+++ b/README
@@ -82,7 +82,8 @@ it. Using other VCSes should be broadly similar.
 
 The `etckeeper init` command initialises an /etc/.git/ repository. This
 command is careful to never overwrite existing files or directories in
-/etc. It will create a `.gitignore` if one doesn't already exist, sets up
+/etc. It will create a `.gitignore` if one doesn't already exist
+(or update content inside a "managed by etckeeper" comment block), sets up
 pre-commit hooks if they don't already exist, and so on. It does *not*
 commit any files, but does `git add` all interesting files for an initial
 commit later.
diff --git a/debian/changelog b/debian/changelog
index 2ab4c30..15feb06 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -3,6 +3,10 @@ etckeeper (0.30) UNRELEASED; urgency=low
   * Add vim .*.sw? files to default ignores.
   * Also add emacs #*# autosave files to default ignores.
   * And DEADJOE files, for good measure.
+  * etckeeper update-ignore will automatically update the VCS ignore
+    file, only touching the part inside a "managed by etckeeper"
+    comment block.
+  * Run etckeeper update-ignore on upgrade.
 
  -- Joey Hess <joeyh@debian.org>  Fri, 13 Feb 2009 22:09:28 -0500
 
diff --git a/debian/postinst b/debian/postinst
index 039c4c0..834b069 100644
--- a/debian/postinst
+++ b/debian/postinst
@@ -72,4 +72,7 @@ configure)
 			fi
 		done
 	fi
+
+	# prints error and exits nonzero if the ignore file cannot be updated
+	etckeeper update-ignore || true
 esac
diff --git a/etckeeper.8 b/etckeeper.8
index 33f511f..cfb6828 100644
--- a/etckeeper.8
+++ b/etckeeper.8
@@ -39,6 +39,11 @@ repository. (You can also call this by hand after running dpkg by hand.)
 .TP
 .B unclean
 This returns true if the directory contains uncommitted changes.
+.TP
+.B update-ignore
+This updates the VCS ignore file. Content outside a "managed by etckeeper"
+block is not touched. This is generally run when upgrading to a new version
+of etckeeper.
 .SH FILES
 /etc/etckeeper/etckeeper.conf is the configuration file.
 
diff --git a/init.d/50vcs-ignore b/init.d/50vcs-ignore
index 3049b95..bcc88ba 100755
--- a/init.d/50vcs-ignore
+++ b/init.d/50vcs-ignore
@@ -1,104 +1,4 @@
 #!/bin/sh
 set -e
 
-if [ "$VCS" = git ] && [ ! -e .gitignore ]; then
-	file=.gitignore
-elif [ "$VCS" = hg ] && [ ! -e .hgignore ]; then
-	file=.hgignore
-elif [ "$VCS" = bzr ] && [ ! -e .bzrignore ]; then
-	file=.bzrignore
-elif [ "$VCS" = darcs ] && [ ! -e .darcsignore ]; then
-	file=.darcsignore
-fi
-
-if [ -z "$file" ] || [ -e "$file" ]; then
-	exit 0
-fi
-
-nl() {
-	echo >>$file
-}
-
-comment() {
-	comment="$1"
-	echo "# $comment" >>$file
-}
-
-ignore() {
-	glob="$1"
-	
-	case "$VCS" in
-		git|bzr)
-			echo "$glob" >> $file
-		;;
-		hg)
-			# rather than converting the glob to a regexp, just
-			# configure hg to use globs
-			if [ -z "$hg_syntax_printed" ]; then
-				comment "use glob syntax"
-				echo "syntax: glob" >> $file
-				nl
-				hg_syntax_printed=1
-			fi
-			echo "$glob" >> $file
-		;;
-		darcs)
-			# darcs doesn't understand globs, so we need to translate
-			# them into regexs. Not a complete converter, but suitable
-			# for given globs.
-			if [ "${glob%\*}" != "$glob" ]; then
-				glob="${glob%\*}"
-			else
-				glob="$glob"'($|/)'
-			fi
-			if [ "${glob#\*}" != "$glob" ]; then
-				glob="${glob#\*}"
-			else
-				glob='(^|/)'"$glob"
-			fi
-			glob="$( printf %s $glob | sed -e 's/\./\\./g;s/\*/[^\/]*/g;s/\?/[^\/]/g' )"
-			echo "$glob" >> $file
-	esac
-}
-
-if [ "$VCS" = darcs ]; then
-	darcs setpref boringfile .darcsignore
-fi
-
-if [ "$LOWLEVEL_PACKAGE_MANAGER" = dpkg ]; then
-	comment "new and old versions of conffiles, stored by dpkg"
-	ignore "*.dpkg-*"
-	nl
-elif [ "$LOWLEVEL_PACKAGE_MANAGER" = "rpm" ]; then
-	comment "new and old versions of conffiles, stored by apt/rpm"
-	ignore "*.rpm*"
-	nl
-elif [ "$LOWLEVEL_PACKAGE_MANAGER" = "pacman-g2" ]; then
-	comment "new and old versions of conffiles, stored by pacman"
-	ignore "*.pacnew"
-	ignore "*.pacorig"
-	ignore "*.pacsave"
-	nl
-fi
-
-comment "mount(8) records system state here, no need to store these"
-ignore blkid.tab
-ignore blkid.tab.old
-nl
-
-comment "some other files in /etc that typically do not need to be tracked"
-ignore nologin
-ignore ld.so.cache
-ignore mtab
-ignore .pwd.lock
-ignore network/run
-ignore adjtime
-ignore lvm/cache
-nl
-
-comment "editor temp files"
-ignore "*~"
-ignore ".*.sw?"
-ignore "#*#"
-ignore DEADJOE
-nl
+etckeeper update-ignore || true
diff --git a/update-ignore.d/01update-ignore b/update-ignore.d/01update-ignore
new file mode 100755
index 0000000..0d4edf8
--- /dev/null
+++ b/update-ignore.d/01update-ignore
@@ -0,0 +1,152 @@
+#!/bin/sh
+set -e
+
+if [ "$VCS" = git ]; then
+	dir=.git
+	file=.gitignore
+elif [ "$VCS" = hg ]; then
+	dir=.hg
+	file=.hgignore
+elif [ "$VCS" = bzr ]; then
+	dir=.bzr
+	file=.bzrignore
+elif [ "$VCS" = darcs ]; then
+	dir=_darcs
+	file=.darcsignore
+else
+	echo "etckeeper: unsupported VCS $VCS" >&2
+	exit 1
+fi
+
+if [ ! -d "$dir" ]; then
+	exit 0
+fi
+
+managed_by_etckeeper="managed by etckeeper"
+
+nl() {
+	echo >>"$file"
+}
+
+comment() {
+	comment="$1"
+	echo "# $comment" >>"$file"
+}
+
+ignore() {
+	glob="$1"
+	
+	case "$VCS" in
+		git|bzr)
+			echo "$glob" >>"$file"
+		;;
+		hg)
+			# rather than converting the glob to a regexp, just
+			# configure hg to use globs
+			if [ -z "$hg_syntax_printed" ]; then
+				comment "use glob syntax"
+				echo "syntax: glob" >>"$file"
+				nl
+				hg_syntax_printed=1
+			fi
+			echo "$glob" >>"$file"
+		;;
+		darcs)
+			# darcs doesn't understand globs, so we need to translate
+			# them into regexs. Not a complete converter, but suitable
+			# for given globs.
+			if [ "${glob%\*}" != "$glob" ]; then
+				glob="${glob%\*}"
+			else
+				glob="$glob"'($|/)'
+			fi
+			if [ "${glob#\*}" != "$glob" ]; then
+				glob="${glob#\*}"
+			else
+				glob='(^|/)'"$glob"
+			fi
+			glob="$( printf %s $glob | sed -e 's/\./\\./g;s/\*/[^\/]*/g;s/\?/[^\/]/g' )"
+			echo "$glob" >>"$file"
+	esac
+}
+
+writefile () {
+	comment "begin section $managed_by_etckeeper (do not edit this section by hand)"
+	nl
+
+	if [ "$VCS" = darcs ]; then
+		darcs setpref boringfile .darcsignore
+	fi
+
+	if [ "$LOWLEVEL_PACKAGE_MANAGER" = dpkg ]; then
+		comment "new and old versions of conffiles, stored by dpkg"
+		ignore "*.dpkg-*"
+		nl
+	elif [ "$LOWLEVEL_PACKAGE_MANAGER" = "rpm" ]; then
+		comment "new and old versions of conffiles, stored by apt/rpm"
+		ignore "*.rpm*"
+		nl
+	elif [ "$LOWLEVEL_PACKAGE_MANAGER" = "pacman-g2" ]; then
+		comment "new and old versions of conffiles, stored by pacman"
+		ignore "*.pacnew"
+		ignore "*.pacorig"
+		ignore "*.pacsave"
+		nl
+	fi
+	
+	comment "mount(8) records system state here, no need to store these"
+	ignore blkid.tab
+	ignore blkid.tab.old
+	nl
+	
+	comment "some other files in /etc that typically do not need to be tracked"
+	ignore nologin
+	ignore ld.so.cache
+	ignore mtab
+	ignore .pwd.lock
+	ignore network/run
+	ignore adjtime
+	ignore lvm/cache
+	nl
+	
+	comment "editor temp files"
+	ignore "*~"
+	ignore ".*.sw?"
+	ignore "#*#"
+	ignore DEADJOE
+
+	nl
+	comment "end section $managed_by_etckeeper"
+}
+
+if [ -e "$file" ]; then
+	if ! grep -q "$managed_by_etckeeper" "$file"; then
+		echo "etckeeper: "$file" does not contain \"$managed_by_etckeeper\" comment; not updating"
+		exit 1
+	fi
+	realfile="$file"
+	file=$(tempfile)
+	(
+		skipping=
+		while read line; do
+			if echo "$line" | grep -q "$managed_by_etckeeper"; then
+				if [ ! "$skipping" ]; then
+					skipping=1
+				else
+					skipping=
+					writefile
+				fi
+			elif [ ! "$skipping" ]; then
+				echo "$line" >> "$file"
+			fi
+		done
+		if [ "$skipping" ]; then
+			# reached end of file w/o ending block
+			writefile
+		fi
+	) <"$realfile"
+
+	mv -f "$file" "$realfile"
+else
+	writefile
+fi
diff --git a/update-ignore.d/README b/update-ignore.d/README
new file mode 100644
index 0000000..a573135
--- /dev/null
+++ b/update-ignore.d/README
@@ -0,0 +1,2 @@
+Executable files in this directory are run to update the VCS ignore file,
+or create it if it does not exist.