git-writehash

#!/bin/bash
# Author: Gokberk Cinbis, 2017
set -e

function helpandpanic()
{
    echo 'git-writehash <file>'
    echo 'Echo git hash'
    echo ''   
    echo 'git-writehash <file>'
    echo 'Write git hash into a file. Exists if file already exists. Writes <hash>_modified if there are uncommitted changes '
    echo ''   
    echo 'EXIT CODES'
    echo '  0 normally'
    echo '  1 if there are uncommited changes'
    echo '  2 if <file> already exists'
    echo '  3 if the number of input args is invalid'
    echo '  other if a subprocess fails (eg, not a git repository)'
    echo ''   
    echo 'SUGGESTED USE'   
    echo 'Call git-uniqueid to generate a log directory in the beginning of an experiment script'   
    echo 'Call git-writehash to write the current hash into a file into the log directory'
    echo 'Call git-checkhash at test time to make sure that the right revision is being used at evaluation time (if necessary)'
    echo ''   
    echo 'PACKAGE'
    echo 'git-uniqueid    Generate a unique log file/directory name for running an experiment'
    echo 'git-writehash   Write git hash into a file'
    echo 'git-checkhash   Check whether the current git hash to make sure the right code-base is being used for evaluating a pre-trained model'
    exit 3
}

# NO! cmd='command git rev-list --full-history --all | head -1' 
# If we've checkout an old revision (ie. in detached-HEAD state), this returns an incorrect result.
h=$(command git rev-parse --verify HEAD)
# not a git repository: git-writehash returns 128.

if [[ -z $(command git status -s) ]]; then # see https://stackoverflow.com/questions/3878624/how-do-i-programmatically-determine-if-there-are-uncommited-changes
    rc=0 # return code
else
    h=${h}_modified
    rc=1 # return code
fi

if [ "$#" -eq 0 ]; then
    echo $h 
    exit $rc
elif [ "$#" -eq 1 ]; then
    file="$1"
    if [ -f "$file" ]
    then
        echo "git-writehash: "$file" already exists. First delete existing output file."
        exit 1
    fi
    echo $h > "$file"
    exit $rc
else
    helpandpanic
fi