patchDocumentation: explain "mboxrd" pretty format

> +++ b/Documentation/pretty-formats.txt
> @@ -83,6 +83,12 @@ placeholders, its output is not affected by other options like
>  
>  	  <full commit message>
>  
> +* 'mboxrd'
> ++
> +Like 'email', but lines in the commit message starting with "From "
> +(preceded by zero or more ">") are quoted with ">" so they aren't
> +confused as starting a new commit.
> +

> The "mboxrd" pretty format was introduced in 9f23e04061 (pretty: support
> "mboxrd" output format, 2016-06-05) but wasn't mentioned in the
> documentation.
>
> Signed-off-by: Emma Brooks <me@pluvano.com>
> ---
>  Documentation/pretty-formats.txt | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
> index a4b6f49186..547a552463 100644
> --- a/Documentation/pretty-formats.txt
> +++ b/Documentation/pretty-formats.txt
> @@ -83,6 +83,12 @@ placeholders, its output is not affected by other options like
>  
>  	  <full commit message>
>  
> +* 'mboxrd'
> ++
> +Like 'email', but lines in the commit message starting with "From "
> +(preceded by zero or more ">") are quoted with ">" so they aren't
> +confused as starting a new commit.

> > +Like 'email', but lines in the commit message starting with "From "
> > +(preceded by zero or more ">") are quoted with ">" so they aren't
> > +confused as starting a new commit.
> 
> I am torn between rephrasing "starting a new commit" with "starting
> a new e-mail message", and keeping it as-is.  Technically, the latter
> is more correct---the >From quoting is a technique to avoid starting
> a line with "From " in a reversible way, as pieces of e-mails in a
> single mailbox file needs to be split at the boundary.  But in the
> context of format-patch, perhaps saying each "record" in the output
> file is a "commit" (not a piece of e-mail message) would probably be
> an acceptable white lie.

> On 2020-04-15 22:03:36-0700, Junio C Hamano wrote:
>> > +Like 'email', but lines in the commit message starting with "From "
>> > +(preceded by zero or more ">") are quoted with ">" so they aren't
>> > +confused as starting a new commit.
>> 
>> I am torn between rephrasing "starting a new commit" with "starting
>> a new e-mail message", and keeping it as-is.  Technically, the latter
>> is more correct---the >From quoting is a technique to avoid starting
>> a line with "From " in a reversible way, as pieces of e-mails in a
>> single mailbox file needs to be split at the boundary.  But in the
>> context of format-patch, perhaps saying each "record" in the output
>> file is a "commit" (not a piece of e-mail message) would probably be
>> an acceptable white lie.
>
> While it is more accurate to say "starting a new email" rather than
> "commit", I think it might be less confusing to say "starting a new
> commit", if the reader isn't already familiar with how mbox works or its
> variants, since the pretty formats control commit display and would
> typically be thought about in terms of commits rather than emails.