Correct the behavior of `dd` when multiple arguments are provided.
Before this commit, if the multiple arguments was provided then
the validation error are returned.
For example
```
$ printf '' | ./target/debug/dd status=none status=noxfer
error: The argument '--status=<LEVEL>' was provided more than once, but cannot be used multiple times
USAGE:
dd [OPTIONS]
For more information try --help
```
The unittest was added for this case.
Since JSON formally cannot contain comments, GitHub highlights comments
in JSON files as errors, but the configuration files for VS Code
in this repository contain comments. This commit configures GitHub to
use a different syntax highlighter for the affected files.
This avoids hacking around the short options of these command line
arguments that have been introduced by clap. Additionally, we test and
correctly handle the combination of both version and help. The GNU
binary will ignore both arguments in this case while clap would perform
the first one. A test for this edge case was added.
Now treats recognized command line options and ignores unrecognized
command line options instead of returning a special exit status for
them.
There is one point of interest, which is related to an implementation
detail in GNU `true`. It may return a non-true exit status (in
particular EXIT_FAIL) if writing the diagnostics of a GNU specific
option fails. For example `true --version > /dev/full` would fail and
have exit status 1.
This behavior was acknowledged in gnu in commit
<9a6a486e6503520fd2581f2d3356b7149f1b225d>. No further
justification provided for keeping this quirk.
POSIX knows no such options, and requires an exit status of 0 in all
cases. We replicate GNU here which is a consistency improvement over the
prior implementation. Adds documentation to clarify the intended
behavior more properly.
Exit with status code 1 for argument parsing errors in `truncate`. When
`clap` encounters an error during argument parsing, it exits with status
code 2. This causes some GNU tests to fail since they expect status code
1.
Refactor the `Mode` enum in the `head.rs` module so that it includes
not only the mode type---lines or bytes---but also whether to read the
first NUM items of that type or all but the last NUM. Before this
commit, these two pieces of information were stored separately. This
made it difficult to read the code through several function calls and
understand at a glance which strategy was being employed.
This allows for `-t` to take invalid unicode (but still single-byte) values
on unix-like platforms. Other platforms, which as of the time of this commit
do not support `OsStr::as_bytes()`, could possibly be supported in the future,
but would require design decisions as to what that means.
