git-version-gen

#!/bin/bash
#
# Extract version information from git, or the version file
# if git is not available
#
#    Usage: git-version-gen <version.h> <.version>
#
# We assume annotated tags will be of the form:
#	vMAJOR.MINOR.PATCHLEVEL
# so git-describe will output something like:
#	v0.9.0-4-g2e1f1b2
# that we'll interpret as:
#	vMAJOR.MINOR.PATCHLEVEL-REL-HASH
#
# The parsed version will be stored in <.version> file as a list:
# 	MAJOR MINOR PL REL HASH DIRTYFLAG
# If git is not available, and the info is read from .version,
# DIRTYFLAG will be forced to 1.
#
# Given the above information, VERSION_STRING will be constructed
# as follows:
#
#   $MAJOR.$MINOR[.$PL][-$REL][.$HASH[.dirty-$DIFFSHA]]
#
# HACK: Stores the full version string to .version.fn (for loading
# by CMake)
#

mkdir -p `dirname $1` || exit -1
ID=`basename $1 | md5sum | cut -f 1 -d ' '`

if which git 2>&1 > /dev/null && git rev-parse --git-dir > /dev/null 2>&1; then
	# Derive version info from git, and store it to .version
	VERSION=`git describe`

	# Parse vMAJ[.MIN][.PL][-REL[-HASH]] format -- the horrific perl script below
	# returns a list consisting of (MAJ MIN PL REL HASH) if it succeeds to parse it, with MIN and PL set to zero if they're not present
	VLIST=(`echo "$VERSION" | perl -e '$_=<>; ($maj,$min,$pl,$rel,$has) = ($_ =~ /^v(\d+)(?:\.(\d+))?(?:\.(\d+))?(?:-(\d+)(?:-g([0-9a-f]+))?)?$/); if("$maj" ne "") {$min+=0; $pl+=0}; print "$maj $min $pl $rel $has"'`)
	if [ ${#VLIST[*]} -eq 0 ]; then
		# Fall back to TAG-REL-HASH format
		# We'll set the version to 0.0.0-REL-HASH
		VLIST=(`echo "$VERSION" | perl -e '$_=<>; ($tag,$rel,$has) = ($_ =~ /^(\w+)(?:-(\d+)(?:-g([0-9a-f]+))?)?$/); print "$tag $rel $has"'`)
		VLIST=(0 0 0 ${VLIST[1]} ${VLIST[2]})
	fi

	DIFFSHA=`git diff | sha1sum | cut -b 1-8`
	if [ "$DIFFSHA" == "da39a3ee" ]; then  # first 8 characters of an empty string hash
		VLIST[5]=0
	else
		VLIST[5]=1
		VLIST[6]="$DIFFSHA"
	fi

	STOREVLIST=1
else
	# Derive version info from .version file, appending
	# the name of the current user
	VLIST=( `cat "$2"` )
	# Force the dirty tag when built out-of-repo
	VLIST[5]=1
fi

MAJ=${VLIST[0]:-0}
MIN=${VLIST[1]:-0}
PL=${VLIST[2]:-0}
REL=${VLIST[3]:-0}
HASH=${VLIST[4]:-00000000}
DIRTY=${VLIST[5]:-1}

if [ "$STOREVLIST" == "1" ]; then
	echo -n "$MAJ $MIN $PL $REL $HASH $DIRTY" > $2
fi

# Construct version string
VERSION="$MAJ.$MIN.$PL"
test "x$REL" != "x" -a "$REL" != "0" && VERSION="$VERSION-$REL"
test "$HASH" != "00000000" && VERSION="${VERSION}.$HASH"
test "$DIRTY" != "0" && VERSION="${VERSION}.dirty"
test "$DIRTY" != "0" -a "x$DIFFSHA" != "x" && VERSION="${VERSION}-$DIFFSHA"

echo -n "$VERSION" > $2.fn

# Generate version.h
echo "#ifndef version_h__$ID" >  $1.tmp
echo "#define version_h__$ID" >>  $1.tmp
echo >> $1.tmp
echo "#define VERSION_STRING \"$VERSION\"" >> $1.tmp
test "$DIRTY" != "0" -a "x$DIFFSHA" != "x" && echo "#define SOURCE_DIRTY \"$DIFFSHA\"" >> $1.tmp
echo >> $1.tmp
echo "#endif // version_h__$ID" >>  $1.tmp

# Replace the old version.h with the new one, if it changed
test -f $1 || touch $1
cmp -s $1.tmp $1 || mv $1.tmp $1
rm -f $1.tmp