Binary

Changes:

The message formatting for the "show" subcommand was improved.
In filter-specs for the "list" subcommand, a '=' is used for separating key
and value when filtering for an exact value, rather than a ':'.

Added features:

The "create-message", "new", "reply" and "tag" now accept the "--author" and
"--date" options. Analogue to the options of "git commit" with the same name,
the new options alter the author and authoring date of the resulting message.
New "reporter-name" and "reporter-email" filter keys for issue filtering
using the "list" subcommand. As the name suggests, the keys may be used for
filtering issues based on the reporter's name or email.
Filter specs for the "list" subcommand can now be used for filtering by
substring or presence of a piece of issue metadata.
Filter specs for the "list" subcommand can now be inverted.

Bug-fixes:

Git-dit did not handle pager and editor flags correctly. For example,
configuring less -R as the pager (contrary to less) would cause git-dit
search for a binary named "less -R", resulting in an error.

Library

Changes:

LineIteratorExt::stripped() now returns an iterator which also strips
trailing blank lines.
Issue::new() now returns a Result.
Multi-line trailers parsed by the Blocks iterator are represented as String
TrailerValue with newlines separating the individual lines from the input.
trailer was promoted to a top-level module.
message::accumulation was moved to trailer
message::metadata was moved to trailer and renamed to spec.
MetadataSpecification was renames to TrailerSpec.
PairsToTrailers and DitTrailers iterator was moved to new
trailers::iter module.
Trailers iterator was moved to message::block module.
DitTrailers is now a generic iterator adapter on top of an iterator over
Trailers.

Added features:

New TrailingBlankTrimmer for removing trailing blank lines from sequences
of lines.
New StrippingIter for stripping messages of comments and unnecessary white
space.
New TrailerFilter type for filtering based on trailers.
New ValueMatcher type for matching TrailerValues.
New MessagesExt convenience trait for iterators over messages. The trait
provides accumulation functionality.
New MultiAccumulator trait for map-based accumulation of multiple trailers.
Implemented Default for TrailerValue.
Implemented Clone for ValueAccumulator.
Implemented From<Blocks> for Trailers

Add documentation of internals as a README.md to the sources of both the
binary and the library.