Convert flashrom to git

- Drop support for Subversion in the getrevision script and Makefile.
 - Add .gitignore and .gitattributes file (the latter to limit exports).
 - Restore modification dates of the exported files from the SCM.
 - Stop exporting SCM log dumps to CHANGELOG. This makes no sense.
 - Do not export the pre-"compiled" manpage. It can be generated like
   anything else from the code dump when we export the respective
   variable.
   The latter is added with this change.
 - Add some initial client-side git hooks
   * When committing check for obvious stuff you never want anyway:
     - white space errors
   * When pushing to the upstream repository check mandatory rules:
      - existing signoffs and acks in all new commits
      - no deletions or creation of branches
      - do not rewrite history of the precious branches, even if forced

NOTE: This patch is adapted from Stefan Tauner's original commit:
https://mail.coreboot.org/pipermail/flashrom/2016-November/014877.html

There are a few major differences:
- This uses coreboot's commit-msg hook which includes support for
  generating and appending Change-Id.
- djgpp-dos target removal is moved to a follow-up patch.
- Version string changes are moved to a follow-up patch.

Change-Id: I64eef21982cac0a0a7419bcd2c8a936672ae9cb2
Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Signed-off-by: David Hendricks <dhendricks@fb.com>
Reviewed-on: https://review.coreboot.org/19206
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/git-hooks/install.sh

@@ -0,0 +1,19 @@
+#!/bin/sh -e
+
+root=$(git rev-parse --show-cdup 2>/dev/null) || \
+     { echo "Not under git control. Cannot install git hooks." >&2 ; exit 0 ; }
+
+dst="${root}"$(git rev-parse --git-path hooks/)
+src=util/git-hooks/ # relative to root
+hooks=$(cd "${root}${src}" && git ls-files -c | grep -Ev 'install.sh|wrapper.sh')
+
+for h in $hooks; do
+	# Test if hook is not already installed, i.e. doesn't point at the wrapper
+	if [ ! "${dst}$h" -ef "${root}${src}wrapper.sh" ]; then
+		# preserve custom hooks if any
+		if [ -e "${dst}$h" ]; then
+			mv "${dst}$h" "${dst}$h.local"
+		fi
+		ln -s "$(git rev-parse --prefix $(git rev-parse --git-path hooks/) --show-cdup)${src}wrapper.sh" "${dst}$h"
+	fi
+done