This patch modifies the GenMarkdownCustom to skip writing a Synopsis
header with the `cmd.Short` duplicated both before and after the header.
Instead, it only writes the `### Synopsis` header and the paragraph when
a `cmd.Long` has some kind of content in it.
Adds `TestGenMdDocWithNoLongOrSynopsis` as the test case.
Signed-off-by: Marc Lopez <marc5.12@outlook.com>
This code was already using io.Writer, but was completely ignoring write
errors.
The most worrying part is how GenMarkdownTreeCustom used an unnecessary
buffer to then dump all of its contents on a file, and instead of
returning an error on file creation/writing, it would just exit the
entire program.
* Move man_docs and md_docs into new doc pkg
* Replace *bytes.Buffer with io.Writer
* Replace c == cmd.helpCommand with c.IsHelpCommand()
* Remove redundant len(children) == 0 check in HasSeeAlso
* Duplicate test setup for doc generation
