Add maintainer update script

This script captures my process for merging changes from new upstream
elfutils releases. It isn't obfuscated for portability as it is only
intended for maintainer use and documentation.

Makefile

@@ -23,7 +23,7 @@ clean:
 libelf.a: $(LIBOBJS) Makefile
 	$(AR) rcs $@ $(LIBOBJS)
 
-libelf.so: $(PICOBJS) Makefile 
+libelf.so: $(PICOBJS) Makefile
 	$(CC) $(LDFLAGS) -shared -Wl,-soname,libelf.so.$(MAJOR) \
 	  -o $@ $(PICOBJS) $(LDLIBS)
 

update

@@ -0,0 +1,57 @@
+#!/bin/bash
+
+set -e -o pipefail
+shopt -s dotglob extglob nullglob
+cd -- "$(git -C "${0%/*}" rev-parse --show-toplevel)"
+
+if [[ $@ != +([0-9])*(.+([0-9])) ]]; then
+  echo "Usage: ${0##*/} UPSTREAM-VERSION"
+  echo "Update upstream branch then merge changes into master."
+  echo "This maintainer script does not attempt to be portable."
+  exit 64
+elif ! git diff --exit-code --quiet; then
+  echo "Uncommitted changes in the working directory"
+  exit 1
+elif ! git diff --cached --exit-code --quiet; then
+  echo "Uncommitted changes in the index"
+  exit 1
+fi >&2
+
+TMP=$(mktemp -d tmp-XXXXXX)
+trap 'rm -r $TMP' EXIT
+
+echo "Downloading upstream files for version $1:"
+URL=https://sourceware.org/elfutils/ftp/$1/elfutils-$1.tar.bz2
+COLUMNS=64 curl -L -# "$URL" | tar -x -f - -C $TMP --strip-components=1
+
+git checkout upstream
+git rm -q -r include src
+mkdir -p include src
+
+for FILE in $TMP/libelf/*.[ch] $TMP/lib/crc32.c $TMP/lib/eu-config.h \
+    $TMP/lib/fixedsizehash.h $TMP/lib/next_prime.c $TMP/lib/system.h; do
+  sed ':a;s/[ \t]*$//;/^\n*$/{$d;N;ba}' "$FILE" >"src/${FILE##*/}"
+  git add "src/${FILE##*/}"
+done
+
+git mv src/gelf.h src/libelf.h src/nlist.h include
+
+cp $TMP/COPYING-GPLV2 $TMP/COPYING-LGPLV3 .
+git add COPYING-GPLV2 COPYING-LGPLV3
+
+if git diff --cached --exit-code --quiet; then
+  echo "No upstream changes to merge"
+  git checkout master
+else
+  git commit -m "Update upstream files from elfutils $1"
+  git checkout master
+  git merge --no-commit upstream
+
+  sed -i "s/^MINOR *=.*/MINOR = $1/" Makefile
+  git add Makefile
+  git commit -m "Merge from upstream libelf $1"
+
+  echo "Merged libelf ready to review, build and test"
+  echo "Sign: git tag -m libelf-$1 -s libelf-$1"
+  echo "Push: git push --tags origin upstream master"
+fi