Re: [PATCH] diff: add support for reading files literally with --no-index
- Date: Thu, 3 Jan 2019 18:18:55 -0800
- From: Jonathan Nieder <jrnieder@xxxxxxxxx>
- Subject: Re: [PATCH] diff: add support for reading files literally with --no-index
brian m. carlson wrote:
> In some shells, such as bash and zsh, it's possible to use a command
> substitution to provide the output of a command as a file argument to
> another process, like so:
> diff -u <(printf "a\nb\n") <(printf "a\nc\n")
> However, this syntax does not produce useful results with git diff
Thanks much for fixing this. It's something I've run into, too.
> --- a/Documentation/git-diff.txt
> +++ b/Documentation/git-diff.txt
> @@ -111,6 +111,11 @@ include::diff-options.txt
> "Unmerged". Can be used only when comparing the working tree
> with the index.
> + Read the specified files literally, as `diff` would,
> + dereferencing any symlinks and reading data from pipes.
> + This option only works with `--no-index`.
I may be a minority in this opinion, but I had trouble understanding
what --literally would do from its name. I suspect we can come up
with a better name.
Unfortunately, I'm terrible at coming up with names. :-P
--dereference would be a good name when it comes to symlinks, but
it's not a good name for reading what is on the other side of a pipe.
On the plus side, it matches "diff" and "cp"'s name for the "follow
symbolic links" option.
--plain captures the desire a little better --- we want a plain
read(2) from the file instead of trying to be smart and look at
whether it is e.g. a block device. But in the context of "diff", that
would seem more like an option that affects the output.
What would you think of
- always reading from fifos instead of describing them, since I've
never encountered a use case where people want the latter
- --dereference to control whether to follow symlinks
> --- a/diff-no-index.c
> +++ b/diff-no-index.c
> @@ -75,7 +75,25 @@ static int populate_from_stdin(struct diff_filespec *s)
> return 0;
> -static struct diff_filespec *noindex_filespec(const char *name, int mode)
> +static int populate_literally(struct diff_filespec *s)
> + struct strbuf buf = STRBUF_INIT;
> + size_t size = 0;
> + int fd = xopen(s->path, O_RDONLY);
> + if (strbuf_read(&buf, fd, 0) < 0)
> + return error_errno("error while reading from '%s'", s->path);
> + s->should_munmap = 0;
> + s->data = strbuf_detach(&buf, &size);
> + s->size = size;
> + s->should_free = 1;
> + s->read_literally = 1;
Oh! --read-literally works perfectly for me as a name. :)