sgit/sgit-commit

#! /bin/bash

[[ $# -lt 1 || $# -gt 3 ]] && echo "Usage: $0 TREE [PARENT] [MESSAGE]

Creates a commit object from tree object with sha1 TREE.
PARENT is an optional earlier commit.
MESSAGE is an optional description of the commit."

objdir="$PWD/.git/objects"
[[ ! -d "$objdir" ]] && echo "Please create $objdir, for example by running sgit-init." && exit 1

name="Tim Rice"
email="t.rice@ms.unimelb.edu.au"
seconds=$(date +"%s")
tz=$(date +"%z")

tree="$1"
parent=""
[[ $# -eq 2 ]] && parent=$2
msg=""
[[ $# -eq 3 ]] && msg=$3

tree_dir="$objdir"/$(echo $tree | awk '{print substr($1,1,2)}')
tree_file=$(echo $tree | awk '{print substr($1,3)}')
[[ ! -f "$tree_dir"/"$tree_file" ]] && echo "No object associated with $tree." && exit 1

if [[ -n "$parent" ]]; then
    parent_dir="$objdir"/$(echo $parent | awk '{print substr($1,1,2)}')
    parent_file=$(echo $parent | awk '{print substr($1,3)}')
    [[ ! -f "$parent_dir"/"$parent_file" ]] && echo "No object associated with $parent." && exit 1
fi


function payload() {
    echo tree $tree
    if [[ -n "$parent" ]]; then
        echo parent $parent
    fi
    echo "author $name <$email> $seconds $tz"
    echo "committer $name <$email> $seconds $tz"
    echo; echo $msg
}

# Every object header contains the object type
# followed by the payload byte length terminated 
# with a null byte (\0).
function header() {
    printf "commit $(payload | wc -c)\0"
}

# A commit contains header + payload.
function commit() {
    cat <(header) <(payload)
}


# Determine where to store the object, based on its
# sha1 hash, and create the necessary directory.
sha=$(commit | sha1sum)
dest_dir="$objdir"/$(echo $sha | awk '{print substr($1,1,2)}')
mkdir -p "$dest_dir"
dest_file=$(echo $sha | awk '{print substr($1,3)}')

# Compress the object with zlib.
commit | openssl zlib > "$dest_dir"/"$dest_file"