GetGitHash

#!/bin/sh

# Return git information in a form of -D flags

# This  file was put into the public domain 2015-12-29 by
# John  P.  Hartmann.  You can use it for anything you like,
# as long as this notice remains.

# This script is run in the top build directory from the makefile as it
# is  read.   The relative path to the top source directory is provided
# as  the  argument.   Produces  a  file  of  declares for inclusion in
# version.c only.  Ensure that a null file exists initially.

# Call  git  utilities  to  extrace the current commit hash and write a
# string  that contains the defines required for version.c.  This works
# only  in  an environment where git is installed and the repository is
# cloned  from  github.   No output is produced if the git commands are
# not available or the repository is not under git control.

# When  git  "errors out" it sets exit status 128.  Only exit states up
# to  127  are  portable  (and  you better let the top ones alone.  The
# upshot is that we cannot just do git something.

# You  can  test  this  in  the  source  directory  (where it lives) by
# supplying . as the path to the build directory.

outfile=commitinfo.h
tempfile=temp.$outfile
builddir=$PWD

# Do not be tempted by man date in Linux
id="/* Generated $(date -u) by $0 */"
idlen=$(echo "$id" | wc -c)

chicken ()
{
        echo "Cannot obtain git status:  $*." >&2
}

# Ensure file exists; so that make will resolve the dependency.

if [ ! -r $outfile ] ; then touch $outfile; fi

# Write dummy file up front so that there is always something
(
        echo "$id"
        echo "#define COMMIT_COUNT 0"
        echo "#define COMMIT_MESSAGE \"\""
        echo "#define COMMIT_HASH \"\""
        echo "#define COMMIT_UNTRACKED \"\""
        echo "#define COMMIT_MODIFIED \"\""

) >$tempfile

dogit ()
{
        gitVersionString=$(git --version 2>/dev/null)
        rv=$?
        if [ $rv -eq 127 ] ; then chicken "git is not installed";
        elif [ $rv -ne 0 ] ; then chicken "git --version return value $rv";
        fi

        if [ $rv -ne 0 ] ; then return; fi

        # Go to top source directory
        cd "$1"
        commitCount=$(git log --pretty=oneline | wc -l)
        # These cannot contain metacharacters
        message=$(git log -n 1 --pretty=format:'%H %h %ai')
        commit=$(echo $message | cut -d ' ' -f 1)
        short=$(echo $message | cut -d ' ' -f 2)
        time=$(echo $message | cut -d ' ' -f 3-5)

        msg=$(git log -n 1 --pretty=format:'%s' | cut -c -70 | tr "'" '\"' )

        gitstat=$(git status --porcelain | grep -v -e ' tests/' -e ' html/' -e ' man/' -e ' scripts/' -e ' util/')
        changed=$(echo $gitstat | grep '^[^?!]' | wc -l)
        new=$(echo $gitstat | grep '^?' | wc -l)

        # Return to build directory
        cd -

        (
                echo "$id"
                echo "#define COMMIT_COUNT $commitCount"
                echo "#define COMMIT_MESSAGE \"$msg\""
                echo "#define COMMIT_HASH \"$commit\""
                if [ 0 -eq $new ]
                then
                        echo "#define COMMIT_UNTRACKED \"\""
                else
                        echo "#define COMMIT_UNTRACKED \"  $new untracked files.\""
                fi
                if [ 0 -eq $changed ]
                then
                        echo "#define COMMIT_MODIFIED \"\""
                else
                        echo "#define COMMIT_MODIFIED \"  $changed added/modified/deleted files.\""
                fi

        ) >$tempfile
}

dogit $1

cmp $outfile $tempfile $idlen $idlen >/dev/null 2>&1
rv=$?

if [ $rv -eq 0 ] ;
then
        rm -f $tempfile
else
        mv $tempfile $outfile
fi