tag: generate useful reflog message

[git] / t / test-lib-functions.sh

# Library of functions shared by all tests scripts, included by
# test-lib.sh.
#
# Copyright (c) 2005 Junio C Hamano
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see http://www.gnu.org/licenses/ .

# The semantics of the editor variables are that of invoking
# sh -c "$EDITOR \"$@\"" files ...
#
# If our trash directory contains shell metacharacters, they will be
# interpreted if we just set $EDITOR directly, so do a little dance with
# environment variables to work around this.
#
# In particular, quoting isn't enough, as the path may contain the same quote
# that we're using.
test_set_editor () {
        FAKE_EDITOR="$1"
        export FAKE_EDITOR
        EDITOR='"$FAKE_EDITOR"'
        export EDITOR
}

test_set_index_version () {
    GIT_INDEX_VERSION="$1"
    export GIT_INDEX_VERSION
}

test_decode_color () {
        awk '
                function name(n) {
                        if (n == 0) return "RESET";
                        if (n == 1) return "BOLD";
                        if (n == 30) return "BLACK";
                        if (n == 31) return "RED";
                        if (n == 32) return "GREEN";
                        if (n == 33) return "YELLOW";
                        if (n == 34) return "BLUE";
                        if (n == 35) return "MAGENTA";
                        if (n == 36) return "CYAN";
                        if (n == 37) return "WHITE";
                        if (n == 40) return "BLACK";
                        if (n == 41) return "BRED";
                        if (n == 42) return "BGREEN";
                        if (n == 43) return "BYELLOW";
                        if (n == 44) return "BBLUE";
                        if (n == 45) return "BMAGENTA";
                        if (n == 46) return "BCYAN";
                        if (n == 47) return "BWHITE";
                }
                {
                        while (match($0, /\033\[[0-9;]*m/) != 0) {
                                printf "%s<", substr($0, 1, RSTART-1);
                                codes = substr($0, RSTART+2, RLENGTH-3);
                                if (length(codes) == 0)
                                        printf "%s", name(0)
                                else {
                                        n = split(codes, ary, ";");
                                        sep = "";
                                        for (i = 1; i <= n; i++) {
                                                printf "%s%s", sep, name(ary[i]);
                                                sep = ";"
                                        }
                                }
                                printf ">";
                                $0 = substr($0, RSTART + RLENGTH, length($0) - RSTART - RLENGTH + 1);
                        }
                        print
                }
        '
}

lf_to_nul () {
        perl -pe 'y/\012/\000/'
}

nul_to_q () {
        perl -pe 'y/\000/Q/'
}

q_to_nul () {
        perl -pe 'y/Q/\000/'
}

q_to_cr () {
        tr Q '\015'
}

q_to_tab () {
        tr Q '\011'
}

qz_to_tab_space () {
        tr QZ '\011\040'
}

append_cr () {
        sed -e 's/$/Q/' | tr Q '\015'
}

remove_cr () {
        tr '\015' Q | sed -e 's/Q$//'
}

# In some bourne shell implementations, the "unset" builtin returns
# nonzero status when a variable to be unset was not set in the first
# place.
#
# Use sane_unset when that should not be considered an error.

sane_unset () {
        unset "$@"
        return 0
}

test_tick () {
        if test -z "${test_tick+set}"
        then
                test_tick=1112911993
        else
                test_tick=$(($test_tick + 60))
        fi
        GIT_COMMITTER_DATE="$test_tick -0700"
        GIT_AUTHOR_DATE="$test_tick -0700"
        export GIT_COMMITTER_DATE GIT_AUTHOR_DATE
}

# Stop execution and start a shell. This is useful for debugging tests and
# only makes sense together with "-v".
#
# Be sure to remove all invocations of this command before submitting.

test_pause () {
        if test "$verbose" = t; then
                "$SHELL_PATH" <&6 >&3 2>&4
        else
                error >&5 "test_pause requires --verbose"
        fi
}

# Wrap git in gdb. Adding this to a command can make it easier to
# understand what is going on in a failing test.
#
# Example: "debug git checkout master".
debug () {
         GIT_TEST_GDB=1 "$@"
}

# Call test_commit with the arguments "<message> [<file> [<contents> [<tag>]]]"
#
# This will commit a file with the given contents and the given commit
# message, and tag the resulting commit with the given tag name.
#
# <file>, <contents>, and <tag> all default to <message>.

test_commit () {
        notick= &&
        signoff= &&
        while test $# != 0
        do
                case "$1" in
                --notick)
                        notick=yes
                        ;;
                --signoff)
                        signoff="$1"
                        ;;
                *)
                        break
                        ;;
                esac
                shift
        done &&
        file=${2:-"$1.t"} &&
        echo "${3-$1}" > "$file" &&
        git add "$file" &&
        if test -z "$notick"
        then
                test_tick
        fi &&
        git commit $signoff -m "$1" &&
        git tag "${4:-$1}"
}

# Call test_merge with the arguments "<message> <commit>", where <commit>
# can be a tag pointing to the commit-to-merge.

test_merge () {
        test_tick &&
        git merge -m "$1" "$2" &&
        git tag "$1"
}

# This function helps systems where core.filemode=false is set.
# Use it instead of plain 'chmod +x' to set or unset the executable bit
# of a file in the working directory and add it to the index.

test_chmod () {
        chmod "$@" &&
        git update-index --add "--chmod=$@"
}

# Unset a configuration variable, but don't fail if it doesn't exist.
test_unconfig () {
        config_dir=
        if test "$1" = -C
        then
                shift
                config_dir=$1
                shift
        fi
        git ${config_dir:+-C "$config_dir"} config --unset-all "$@"
        config_status=$?
        case "$config_status" in
        5) # ok, nothing to unset
                config_status=0
                ;;
        esac
        return $config_status
}

# Set git config, automatically unsetting it after the test is over.
test_config () {
        config_dir=
        if test "$1" = -C
        then
                shift
                config_dir=$1
                shift
        fi
        test_when_finished "test_unconfig ${config_dir:+-C '$config_dir'} '$1'" &&
        git ${config_dir:+-C "$config_dir"} config "$@"
}

test_config_global () {
        test_when_finished "test_unconfig --global '$1'" &&
        git config --global "$@"
}

write_script () {
        {
                echo "#!${2-"$SHELL_PATH"}" &&
                cat
        } >"$1" &&
        chmod +x "$1"
}

# Use test_set_prereq to tell that a particular prerequisite is available.
# The prerequisite can later be checked for in two ways:
#
# - Explicitly using test_have_prereq.
#
# - Implicitly by specifying the prerequisite tag in the calls to
#   test_expect_{success,failure,code}.
#
# The single parameter is the prerequisite tag (a simple word, in all
# capital letters by convention).

test_set_prereq () {
        satisfied_prereq="$satisfied_prereq$1 "
}
satisfied_prereq=" "
lazily_testable_prereq= lazily_tested_prereq=

# Usage: test_lazy_prereq PREREQ 'script'
test_lazy_prereq () {
        lazily_testable_prereq="$lazily_testable_prereq$1 "
        eval test_prereq_lazily_$1=\$2
}

test_run_lazy_prereq_ () {
        script='
mkdir -p "$TRASH_DIRECTORY/prereq-test-dir" &&
(
        cd "$TRASH_DIRECTORY/prereq-test-dir" &&'"$2"'
)'
        say >&3 "checking prerequisite: $1"
        say >&3 "$script"
        test_eval_ "$script"
        eval_ret=$?
        rm -rf "$TRASH_DIRECTORY/prereq-test-dir"
        if test "$eval_ret" = 0; then
                say >&3 "prerequisite $1 ok"
        else
                say >&3 "prerequisite $1 not satisfied"
        fi
        return $eval_ret
}

test_have_prereq () {
        # prerequisites can be concatenated with ','
        save_IFS=$IFS
        IFS=,
        set -- $*
        IFS=$save_IFS

        total_prereq=0
        ok_prereq=0
        missing_prereq=

        for prerequisite
        do
                case "$prerequisite" in
                !*)
                        negative_prereq=t
                        prerequisite=${prerequisite#!}
                        ;;
                *)
                        negative_prereq=
                esac

                case " $lazily_tested_prereq " in
                *" $prerequisite "*)
                        ;;
                *)
                        case " $lazily_testable_prereq " in
                        *" $prerequisite "*)
                                eval "script=\$test_prereq_lazily_$prerequisite" &&
                                if test_run_lazy_prereq_ "$prerequisite" "$script"
                                then
                                        test_set_prereq $prerequisite
                                fi
                                lazily_tested_prereq="$lazily_tested_prereq$prerequisite "
                        esac
                        ;;
                esac

                total_prereq=$(($total_prereq + 1))
                case "$satisfied_prereq" in
                *" $prerequisite "*)
                        satisfied_this_prereq=t
                        ;;
                *)
                        satisfied_this_prereq=
                esac

                case "$satisfied_this_prereq,$negative_prereq" in
                t,|,t)
                        ok_prereq=$(($ok_prereq + 1))
                        ;;
                *)
                        # Keep a list of missing prerequisites; restore
                        # the negative marker if necessary.
                        prerequisite=${negative_prereq:+!}$prerequisite
                        if test -z "$missing_prereq"
                        then
                                missing_prereq=$prerequisite
                        else
                                missing_prereq="$prerequisite,$missing_prereq"
                        fi
                esac
        done

        test $total_prereq = $ok_prereq
}

test_declared_prereq () {
        case ",$test_prereq," in
        *,$1,*)
                return 0
                ;;
        esac
        return 1
}

test_verify_prereq () {
        test -z "$test_prereq" ||
        expr >/dev/null "$test_prereq" : '[A-Z0-9_,!]*$' ||
        error "bug in the test script: '$test_prereq' does not look like a prereq"
}

test_expect_failure () {
        test_start_
        test "$#" = 3 && { test_prereq=$1; shift; } || test_prereq=
        test "$#" = 2 ||
        error "bug in the test script: not 2 or 3 parameters to test-expect-failure"
        test_verify_prereq
        export test_prereq
        if ! test_skip "$@"
        then
                say >&3 "checking known breakage: $2"
                if test_run_ "$2" expecting_failure
                then
                        test_known_broken_ok_ "$1"
                else
                        test_known_broken_failure_ "$1"
                fi
        fi
        test_finish_
}

test_expect_success () {
        test_start_
        test "$#" = 3 && { test_prereq=$1; shift; } || test_prereq=
        test "$#" = 2 ||
        error "bug in the test script: not 2 or 3 parameters to test-expect-success"
        test_verify_prereq
        export test_prereq
        if ! test_skip "$@"
        then
                say >&3 "expecting success: $2"
                if test_run_ "$2"
                then
                        test_ok_ "$1"
                else
                        test_failure_ "$@"
                fi
        fi
        test_finish_
}

# test_external runs external test scripts that provide continuous
# test output about their progress, and succeeds/fails on
# zero/non-zero exit code.  It outputs the test output on stdout even
# in non-verbose mode, and announces the external script with "# run
# <n>: ..." before running it.  When providing relative paths, keep in
# mind that all scripts run in "trash directory".
# Usage: test_external description command arguments...
# Example: test_external 'Perl API' perl ../path/to/test.pl
test_external () {
        test "$#" = 4 && { test_prereq=$1; shift; } || test_prereq=
        test "$#" = 3 ||
        error >&5 "bug in the test script: not 3 or 4 parameters to test_external"
        descr="$1"
        shift
        test_verify_prereq
        export test_prereq
        if ! test_skip "$descr" "$@"
        then
                # Announce the script to reduce confusion about the
                # test output that follows.
                say_color "" "# run $test_count: $descr ($*)"
                # Export TEST_DIRECTORY, TRASH_DIRECTORY and GIT_TEST_LONG
                # to be able to use them in script
                export TEST_DIRECTORY TRASH_DIRECTORY GIT_TEST_LONG
                # Run command; redirect its stderr to &4 as in
                # test_run_, but keep its stdout on our stdout even in
                # non-verbose mode.
                "$@" 2>&4
                if test "$?" = 0
                then
                        if test $test_external_has_tap -eq 0; then
                                test_ok_ "$descr"
                        else
                                say_color "" "# test_external test $descr was ok"
                                test_success=$(($test_success + 1))
                        fi
                else
                        if test $test_external_has_tap -eq 0; then
                                test_failure_ "$descr" "$@"
                        else
                                say_color error "# test_external test $descr failed: $@"
                                test_failure=$(($test_failure + 1))
                        fi
                fi
        fi
}

# Like test_external, but in addition tests that the command generated
# no output on stderr.
test_external_without_stderr () {
        # The temporary file has no (and must have no) security
        # implications.
        tmp=${TMPDIR:-/tmp}
        stderr="$tmp/git-external-stderr.$$.tmp"
        test_external "$@" 4> "$stderr"
        test -f "$stderr" || error "Internal error: $stderr disappeared."
        descr="no stderr: $1"
        shift
        say >&3 "# expecting no stderr from previous command"
        if test ! -s "$stderr"
        then
                rm "$stderr"

                if test $test_external_has_tap -eq 0; then
                        test_ok_ "$descr"
                else
                        say_color "" "# test_external_without_stderr test $descr was ok"
                        test_success=$(($test_success + 1))
                fi
        else
                if test "$verbose" = t
                then
                        output=$(echo; echo "# Stderr is:"; cat "$stderr")
                else
                        output=
                fi
                # rm first in case test_failure exits.
                rm "$stderr"
                if test $test_external_has_tap -eq 0; then
                        test_failure_ "$descr" "$@" "$output"
                else
                        say_color error "# test_external_without_stderr test $descr failed: $@: $output"
                        test_failure=$(($test_failure + 1))
                fi
        fi
}

# debugging-friendly alternatives to "test [-f|-d|-e]"
# The commands test the existence or non-existence of $1. $2 can be
# given to provide a more precise diagnosis.
test_path_is_file () {
        if ! test -f "$1"
        then
                echo "File $1 doesn't exist. $2"
                false
        fi
}

test_path_is_dir () {
        if ! test -d "$1"
        then
                echo "Directory $1 doesn't exist. $2"
                false
        fi
}

# Check if the directory exists and is empty as expected, barf otherwise.
test_dir_is_empty () {
        test_path_is_dir "$1" &&
        if test -n "$(ls -a1 "$1" | egrep -v '^\.\.?$')"
        then
                echo "Directory '$1' is not empty, it contains:"
                ls -la "$1"
                return 1
        fi
}

test_path_is_missing () {
        if test -e "$1"
        then
                echo "Path exists:"
                ls -ld "$1"
                if test $# -ge 1
                then
                        echo "$*"
                fi
                false
        fi
}

# test_line_count checks that a file has the number of lines it
# ought to. For example:
#
#       test_expect_success 'produce exactly one line of output' '
#               do something >output &&
#               test_line_count = 1 output
#       '
#
# is like "test $(wc -l <output) = 1" except that it passes the
# output through when the number of lines is wrong.

test_line_count () {
        if test $# != 3
        then
                error "bug in the test script: not 3 parameters to test_line_count"
        elif ! test $(wc -l <"$3") "$1" "$2"
        then
                echo "test_line_count: line count for $3 !$1 $2"
                cat "$3"
                return 1
        fi
}

# Returns success if a comma separated string of keywords ($1) contains a
# given keyword ($2).
# Examples:
# `list_contains "foo,bar" bar` returns 0
# `list_contains "foo" bar` returns 1

list_contains () {
        case ",$1," in
        *,$2,*)
                return 0
                ;;
        esac
        return 1
}

# This is not among top-level (test_expect_success | test_expect_failure)
# but is a prefix that can be used in the test script, like:
#
#       test_expect_success 'complain and die' '
#           do something &&
#           do something else &&
#           test_must_fail git checkout ../outerspace
#       '
#
# Writing this as "! git checkout ../outerspace" is wrong, because
# the failure could be due to a segv.  We want a controlled failure.

test_must_fail () {
        case "$1" in
        ok=*)
                _test_ok=${1#ok=}
                shift
                ;;
        *)
                _test_ok=
                ;;
        esac
        "$@"
        exit_code=$?
        if test $exit_code -eq 0 && ! list_contains "$_test_ok" success
        then
                echo >&2 "test_must_fail: command succeeded: $*"
                return 1
        elif test_match_signal 13 $exit_code && list_contains "$_test_ok" sigpipe
        then
                return 0
        elif test $exit_code -gt 129 && test $exit_code -le 192
        then
                echo >&2 "test_must_fail: died by signal $(($exit_code - 128)): $*"
                return 1
        elif test $exit_code -eq 127
        then
                echo >&2 "test_must_fail: command not found: $*"
                return 1
        elif test $exit_code -eq 126
        then
                echo >&2 "test_must_fail: valgrind error: $*"
                return 1
        fi
        return 0
}

# Similar to test_must_fail, but tolerates success, too.  This is
# meant to be used in contexts like:
#
#       test_expect_success 'some command works without configuration' '
#               test_might_fail git config --unset all.configuration &&
#               do something
#       '
#
# Writing "git config --unset all.configuration || :" would be wrong,
# because we want to notice if it fails due to segv.

test_might_fail () {
        test_must_fail ok=success "$@"
}

# Similar to test_must_fail and test_might_fail, but check that a
# given command exited with a given exit code. Meant to be used as:
#
#       test_expect_success 'Merge with d/f conflicts' '
#               test_expect_code 1 git merge "merge msg" B master
#       '

test_expect_code () {
        want_code=$1
        shift
        "$@"
        exit_code=$?
        if test $exit_code = $want_code
        then
                return 0
        fi

        echo >&2 "test_expect_code: command exited with $exit_code, we wanted $want_code $*"
        return 1
}

# test_cmp is a helper function to compare actual and expected output.
# You can use it like:
#
#       test_expect_success 'foo works' '
#               echo expected >expected &&
#               foo >actual &&
#               test_cmp expected actual
#       '
#
# This could be written as either "cmp" or "diff -u", but:
# - cmp's output is not nearly as easy to read as diff -u
# - not all diff versions understand "-u"

test_cmp() {
        $GIT_TEST_CMP "$@"
}

# test_cmp_bin - helper to compare binary files

test_cmp_bin() {
        cmp "$@"
}

# Call any command "$@" but be more verbose about its
# failure. This is handy for commands like "test" which do
# not output anything when they fail.
verbose () {
        "$@" && return 0
        echo >&2 "command failed: $(git rev-parse --sq-quote "$@")"
        return 1
}

# Check if the file expected to be empty is indeed empty, and barfs
# otherwise.

test_must_be_empty () {
        if test -s "$1"
        then
                echo "'$1' is not empty, it contains:"
                cat "$1"
                return 1
        fi
}

# Tests that its two parameters refer to the same revision
test_cmp_rev () {
        git rev-parse --verify "$1" >expect.rev &&
        git rev-parse --verify "$2" >actual.rev &&
        test_cmp expect.rev actual.rev
}

# Print a sequence of integers in increasing order, either with
# two arguments (start and end):
#
#     test_seq 1 5 -- outputs 1 2 3 4 5 one line at a time
#
# or with one argument (end), in which case it starts counting
# from 1.

test_seq () {
        case $# in
        1)      set 1 "$@" ;;
        2)      ;;
        *)      error "bug in the test script: not 1 or 2 parameters to test_seq" ;;
        esac
        test_seq_counter__=$1
        while test "$test_seq_counter__" -le "$2"
        do
                echo "$test_seq_counter__"
                test_seq_counter__=$(( $test_seq_counter__ + 1 ))
        done
}

# This function can be used to schedule some commands to be run
# unconditionally at the end of the test to restore sanity:
#
#       test_expect_success 'test core.capslock' '
#               git config core.capslock true &&
#               test_when_finished "git config --unset core.capslock" &&
#               hello world
#       '
#
# That would be roughly equivalent to
#
#       test_expect_success 'test core.capslock' '
#               git config core.capslock true &&
#               hello world
#               git config --unset core.capslock
#       '
#
# except that the greeting and config --unset must both succeed for
# the test to pass.
#
# Note that under --immediate mode, no clean-up is done to help diagnose
# what went wrong.

test_when_finished () {
        # We cannot detect when we are in a subshell in general, but by
        # doing so on Bash is better than nothing (the test will
        # silently pass on other shells).
        test "${BASH_SUBSHELL-0}" = 0 ||
        error "bug in test script: test_when_finished does nothing in a subshell"
        test_cleanup="{ $*
                } && (exit \"\$eval_ret\"); eval_ret=\$?; $test_cleanup"
}

# Most tests can use the created repository, but some may need to create more.
# Usage: test_create_repo <directory>
test_create_repo () {
        test "$#" = 1 ||
        error "bug in the test script: not 1 parameter to test-create-repo"
        repo="$1"
        mkdir -p "$repo"
        (
                cd "$repo" || error "Cannot setup test environment"
                "$GIT_EXEC_PATH/git-init" "--template=$GIT_BUILD_DIR/templates/blt/" >&3 2>&4 ||
                error "cannot run git init -- have you built things yet?"
                mv .git/hooks .git/hooks-disabled
        ) || exit
}

# This function helps on symlink challenged file systems when it is not
# important that the file system entry is a symbolic link.
# Use test_ln_s_add instead of "ln -s x y && git add y" to add a
# symbolic link entry y to the index.

test_ln_s_add () {
        if test_have_prereq SYMLINKS
        then
                ln -s "$1" "$2" &&
                git update-index --add "$2"
        else
                printf '%s' "$1" >"$2" &&
                ln_s_obj=$(git hash-object -w "$2") &&
                git update-index --add --cacheinfo 120000 $ln_s_obj "$2" &&
                # pick up stat info from the file
                git update-index "$2"
        fi
}

# This function writes out its parameters, one per line
test_write_lines () {
        printf "%s\n" "$@"
}

perl () {
        command "$PERL_PATH" "$@"
}

# Is the value one of the various ways to spell a boolean true/false?
test_normalize_bool () {
        git -c magic.variable="$1" config --bool magic.variable 2>/dev/null
}

# Given a variable $1, normalize the value of it to one of "true",
# "false", or "auto" and store the result to it.
#
#     test_tristate GIT_TEST_HTTPD
#
# A variable set to an empty string is set to 'false'.
# A variable set to 'false' or 'auto' keeps its value.
# Anything else is set to 'true'.
# An unset variable defaults to 'auto'.
#
# The last rule is to allow people to set the variable to an empty
# string and export it to decline testing the particular feature
# for versions both before and after this change.  We used to treat
# both unset and empty variable as a signal for "do not test" and
# took any non-empty string as "please test".

test_tristate () {
        if eval "test x\"\${$1+isset}\" = xisset"
        then
                # explicitly set
                eval "
                        case \"\$$1\" in
                        '')     $1=false ;;
                        auto)   ;;
                        *)      $1=\$(test_normalize_bool \$$1 || echo true) ;;
                        esac
                "
        else
                eval "$1=auto"
        fi
}

# Exit the test suite, either by skipping all remaining tests or by
# exiting with an error. If "$1" is "auto", we then we assume we were
# opportunistically trying to set up some tests and we skip. If it is
# "true", then we report a failure.
#
# The error/skip message should be given by $2.
#
test_skip_or_die () {
        case "$1" in
        auto)
                skip_all=$2
                test_done
                ;;
        true)
                error "$2"
                ;;
        *)
                error "BUG: test tristate is '$1' (real error: $2)"
        esac
}

# The following mingw_* functions obey POSIX shell syntax, but are actually
# bash scripts, and are meant to be used only with bash on Windows.

# A test_cmp function that treats LF and CRLF equal and avoids to fork
# diff when possible.
mingw_test_cmp () {
        # Read text into shell variables and compare them. If the results
        # are different, use regular diff to report the difference.
        local test_cmp_a= test_cmp_b=

        # When text came from stdin (one argument is '-') we must feed it
        # to diff.
        local stdin_for_diff=

        # Since it is difficult to detect the difference between an
        # empty input file and a failure to read the files, we go straight
        # to diff if one of the inputs is empty.
        if test -s "$1" && test -s "$2"
        then
                # regular case: both files non-empty
                mingw_read_file_strip_cr_ test_cmp_a <"$1"
                mingw_read_file_strip_cr_ test_cmp_b <"$2"
        elif test -s "$1" && test "$2" = -
        then
                # read 2nd file from stdin
                mingw_read_file_strip_cr_ test_cmp_a <"$1"
                mingw_read_file_strip_cr_ test_cmp_b
                stdin_for_diff='<<<"$test_cmp_b"'
        elif test "$1" = - && test -s "$2"
        then
                # read 1st file from stdin
                mingw_read_file_strip_cr_ test_cmp_a
                mingw_read_file_strip_cr_ test_cmp_b <"$2"
                stdin_for_diff='<<<"$test_cmp_a"'
        fi
        test -n "$test_cmp_a" &&
        test -n "$test_cmp_b" &&
        test "$test_cmp_a" = "$test_cmp_b" ||
        eval "diff -u \"\$@\" $stdin_for_diff"
}

# $1 is the name of the shell variable to fill in
mingw_read_file_strip_cr_ () {
        # Read line-wise using LF as the line separator
        # and use IFS to strip CR.
        local line
        while :
        do
                if IFS=$'\r' read -r -d $'\n' line
                then
                        # good
                        line=$line$'\n'
                else
                        # we get here at EOF, but also if the last line
                        # was not terminated by LF; in the latter case,
                        # some text was read
                        if test -z "$line"
                        then
                                # EOF, really
                                break
                        fi
                fi
                eval "$1=\$$1\$line"
        done
}

# Like "env FOO=BAR some-program", but run inside a subshell, which means
# it also works for shell functions (though those functions cannot impact
# the environment outside of the test_env invocation).
test_env () {
        (
                while test $# -gt 0
                do
                        case "$1" in
                        *=*)
                                eval "${1%%=*}=\${1#*=}"
                                eval "export ${1%%=*}"
                                shift
                                ;;
                        *)
                                "$@"
                                exit
                                ;;
                        esac
                done
        )
}

# Returns true if the numeric exit code in "$2" represents the expected signal
# in "$1". Signals should be given numerically.
test_match_signal () {
        if test "$2" = "$((128 + $1))"
        then
                # POSIX
                return 0
        elif test "$2" = "$((256 + $1))"
        then
                # ksh
                return 0
        fi
        return 1
}

# Read up to "$1" bytes (or to EOF) from stdin and write them to stdout.
test_copy_bytes () {
        perl -e '
                my $len = $ARGV[1];
                while ($len > 0) {
                        my $s;
                        my $nread = sysread(STDIN, $s, $len);
                        die "cannot read: $!" unless defined($nread);
                        print $s;
                        $len -= $nread;
                }
        ' - "$1"
}

# run "$@" inside a non-git directory
nongit () {
        test -d non-repo ||
        mkdir non-repo ||
        return 1

        (
                GIT_CEILING_DIRECTORIES=$(pwd) &&
                export GIT_CEILING_DIRECTORIES &&
                cd non-repo &&
                "$@"
        )
}