t4041, t4205, t6006, t7102: use iso8859-1 rather than iso-8859-1

This is actually a fixup of de6029a2d7734a93a9e27b9c4471862a47dd8123,
which was applied before final patch series was sent.

Also, see 3994e8a98dc7bbf67e61d23c8125f44383499a1f for the explanation
of such a replacement.

Signed-off-by: Alexey Shumkin <Alex.Crezoff@gmail.com>
Reviewed-by: Johannes Sixt <j.sixt@viscovery.net>
t4205: revert back single quotes

In previuos commit de6029a2d7734a93a9e27b9c4471862a47dd8123 single
quotes were replaced with double quotes to make "$(commit_msg)"
expression in heredoc to work. The same effect can be achieved by using
"EOF" as a heredoc delimiter instead of "\EOF".

Signed-off-by: Alexey Shumkin <Alex.Crezoff@gmail.com>
Suggested-by: Johannes Sixt <j.sixt@viscovery.net>
t4205, t6006, t7102: make functions more readable

Function 'test_format' is become hard to read after its change in
de6029a2d7734a93a9e27b9c4471862a47dd8123. So, make it more elegant.
Also, change 'commit_msg' function to make it more pretty.

Signed-off-by: Alexey Shumkin <Alex.Crezoff@gmail.com>
Improved-by: Johannes Sixt <j.sixt@viscovery.net>
t6006: add two more tests for the case i18n.commitEncoding is not set

In de6029a2d7734a93a9e27b9c4471862a47dd8123 'complex-subject' test was
changed. Revert it back, and add two more tests to test encoding
conversions with no i18n.commitEncoding set.

Signed-off-by: Alexey Shumkin <Alex.Crezoff@gmail.com>
Reviewed-by: Johannes Sixt <j.sixt@viscovery.net>
t4205: avoid using `sed`

For testing truncated log messages 'commit_msg' function uses `sed` to
cut a message. On various platforms `sed` behaves differently and
results of its work depend on locales installed. So, avoid using `sed`.
Use predefined expected outputs instead of calculated ones.

Signed-off-by: Alexey Shumkin <Alex.Crezoff@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>