Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

The capability to parse a checksum file that has not been ordered into
case-sensitive alphabetical order should not be considered to be a bug
fix, but rather an improvement. It doesn't change anything if the
checksum files have been created by Unaltered, but it can be useful if
they have been created by another tool.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

Make the difference between too few (no command) and too many
arguments.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

In the README file, make it clear that the command is executed in the
current directory. Providing directories in arguments may be risky, if
the ENTER key is pressed too soon by accident, whereas checking the
current directory has to be done before typing the command.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

When computing the checksum with try_digest(), don't use unwrap() which
will panic in case of error (permission denied for example). Instead,
print an explicit error message, and exit with failure.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

If anything went wrong, return a failure exit status.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

In case of error when handling the checksum file, print the explicit
error message.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

Use an enum (List, Update or Check) for the command, instead of two
booleans (update and check). This makes more sense, because the two
booleans cannot both be true at the same time.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

It sounds more natural to list the files that have been removed before
the ones that need to be added.

Therefore, parse the checksum file at first, to detect all the files
that are not present anymore in the directory list. And then parse the
directory list again, to detect all the files that have not been found
and must be added.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

Add CHANGELOG.md file, to describe the changes since the first release.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

If the checksum file is not sorted as expected (case-sensitive
alphabetical order), some files will be detected as removed and added,
and their checksum will be computed again.

This can happen if the checksum file was sorted into case-insensitive
alphabetical order, for example with "sha256sum *" command in a
terminal with en_US.UTF-8 locale.

To avoid this, read all the checksums into an array at the beginning,
and then, when parsing the content of the directory, search for each
file in the whole array, whatever its position.

In the end, reorder the content of the checksum file if necesssary,
even if there is no other change.

The algorithm is slightly less efficient if the checksum files were
created by Unaltered (and thus sorted as expected), but it is more
robust and compatible with checksum files created by other tools.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

Try to make the description and the instructions clearer.

In the README file, provide the detailed steps for typical use cases.
Mention that the alphabetical order is case-sensitive, and that the
checksum files are compatible with sha256sum command.

In the help message, instead of describing the details of each command,
first describe what the expected status is, because it will be checked
by all commands. It simplifies the description of the commands.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

Read the last modification time of each file. If a file is already
listed, but more recent than the checksum file, then it means that the
checksum file is not up to date for this file.

In that case, the file must not be considered altered (bad checksum).
It has obviously been deliberately modified after the checksum file was
created or updated for the last time.

* When using the 'list' or 'check' command, a warning must be printed
  (with the 'check' command it is not even necessary to verify the
  checksum).
* When using the 'update' command, the checksum of the file must be
  updated.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

When the checksum file is created or updated, make sure to set the
read-only permission on it. This file should not be manually edited.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>

With this first version you can create checksum files, update them if
some files are added or removed, and verify the checksums.

Signed-off-by: Cédric Marie <cedric@hjuvi.fr.eu.org>