: included from 6002 and others

mkdir -p .git/refs/tags

>sed.script

# Answer the sha1 has associated with the tag. The tag must exist in .git/refs/tags
tag () {
        _tag=$1
        test -f ".git/refs/tags/$_tag" || error "tag: \"$_tag\" does not exist"
        cat ".git/refs/tags/$_tag"
}

# Generate a commit using the text specified to make it unique and the tree
# named by the tag specified.
unique_commit () {
        _text=$1
        _tree=$2
        shift 2
        echo "$_text" | git commit-tree $(tag "$_tree") "$@"
}

# Save the output of a command into the tag specified. Prepend
# a substitution script for the tag onto the front of sed.script
save_tag () {
        _tag=$1
        test -n "$_tag" || error "usage: save_tag tag commit-args ..."
        shift 1
        "$@" >".git/refs/tags/$_tag"

        echo "s/$(tag $_tag)/$_tag/g" >sed.script.tmp
        cat sed.script >>sed.script.tmp
        rm sed.script
        mv sed.script.tmp sed.script
}

# Replace unhelpful sha1 hashes with their symbolic equivalents
entag () {
        sed -f sed.script
}

# Execute a command after first saving, then setting the GIT_AUTHOR_EMAIL
# tag to a specified value. Restore the original value on return.
as_author () {
        _author=$1
        shift 1
        _save=$GIT_AUTHOR_EMAIL

        GIT_AUTHOR_EMAIL="$_author"
        export GIT_AUTHOR_EMAIL
        "$@"
        if test -z "$_save"
        then
                unset GIT_AUTHOR_EMAIL
        else
                GIT_AUTHOR_EMAIL="$_save"
                export GIT_AUTHOR_EMAIL
        fi
}

commit_date () {
        _commit=$1
        git cat-file commit $_commit |
        sed -n "s/^committer .*> \([0-9]*\) .*/\1/p"
}

# Assign the value of fake date to a variable, but
# allow fairly common "1971-08-16 00:00" to be omittd
assign_fake_date () {
        case "$2" in
        ??:??:??)       eval "$1='1971-08-16 $2'" ;;
        ??:??)          eval "$1='1971-08-16 00:$2'" ;;
        ??)             eval "$1='1971-08-16 00:00:$2'" ;;
        *)              eval "$1='$2'" ;;
        esac
}

on_committer_date () {
        assign_fake_date GIT_COMMITTER_DATE "$1"
        export GIT_COMMITTER_DATE
        shift 1
        "$@"
}

on_dates () {
        assign_fake_date GIT_COMMITTER_DATE "$1"
        assign_fake_date GIT_AUTHOR_DATE "$2"
        export GIT_COMMITTER_DATE GIT_AUTHOR_DATE
        shift 2
        "$@"
}

# Execute a command and suppress any error output.
hide_error () {
        "$@" 2>/dev/null
}

check_output () {
        _name=$1
        shift 1
        if eval "$*" | entag >"$_name.actual"
        then
                test_cmp "$_name.expected" "$_name.actual"
        else
                return 1
        fi
}

# Turn a reasonable test description into a reasonable test name.
# All alphanums translated into -'s which are then compressed and stripped
# from front and back.
name_from_description () {
        perl -pe '
                s/[^A-Za-z0-9.]/-/g;
                s/-+/-/g;
                s/-$//;
                s/^-//;
                y/A-Z/a-z/;
        '
}


# Execute the test described by the first argument, by eval'ing
# command line specified in the 2nd argument. Check the status code
# is zero and that the output matches the stream read from
# stdin.
test_output_expect_success()
{
        _description=$1
        _test=$2
        test $# -eq 2 ||
        error "usage: test_output_expect_success description test <<EOF ... EOF"

        _name=$(echo $_description | name_from_description)
        cat >"$_name.expected"
        test_expect_success "$_description" "check_output $_name \"$_test\""
}