RFR: 8271356: Modify jdb to treat an empty command as a repeat of the previous command [v3]

[Jakob Cornell]

On Tue, 31 Aug 2021 00:36:51 GMT, Jakob Cornell <github.com+5642931+jakobcornell at openjdk.org> wrote:

>> This has been under discussion on and off for the past month or so on serviceability-dev, and I think a CSR request is required, so this may be a work in progress.
>> 
>> Notes on the patch:
>> 
>> - The `list` command previously marked a line in each listing with `=>`.  In a bare `list` this is the next line up for execution.  Previously when requesting a specific location (e.g. `list 5`) the requested line would be marked.  With the patch applied, `list` will only ever mark the next line up for execution.  This is consistent with the behavior of GDB and PDB (at least).
>> - `EOF` is printed when the repeat setting is on and a bare `list` command follows a listing containing the last source line.  This feature is from PDB; it's a somewhat softer message than the one for an explicit `list` request that's out of range.
>> - I don't speak Chinese or Japanese, so I've omitted localizations for the new messages in those locales.  However, I updated the help text in both to include the new commands, with the descriptions left empty for now.
>
> Jakob Cornell has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR.

I've added fairly thorough tests for the new stuff in this branch, including command repetition, list auto-advance, and the tentative new behavior of the `=>` indicator in listings.

Chris, do you think I should give the Chinese and Japanese localizations a shot?  I do actually know a little Chinese, but the Japanese would basically just be whatever Google Translate says.  Or maybe during the CSR review somebody will be able to help?  Not really sure how to proceed.

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PR: https://git.openjdk.java.net/jdk/pull/5290