feat: persistent search history

[amakrushin]

#171 added search history, which resets after quit from revdiff.

Feature request: persistent search history `

It is common practice: less, nvim, Jetbrains IDEs .

Less manual:

     LESSHISTFILE
            Name  of the history file used to remember search commands and shell commands between invocations of
            less.  If set to "-" or "/dev/null", a history file is not used.  The default depends on the operat‐
            ing system, but is usually:

            Linux and Unix
                   "$XDG_STATE_HOME/lesshst"  or  "$HOME/.local/state/lesshst"  or  "$XDG_DATA_HOME/lesshst"  or
                   "$HOME/.lesshst".

            Windows and MS-DOS
                   "$HOME/_lesshst".

            OS/2   "$HOME/lesshst.ini" or "$INIT/lesshst.ini".

[umputun]

honestly not sold on persistent search for revdiff. Never personally found it useful in less or others, and revdiff sessions tend to be short and focused on one diff. Happy to be wrong though, what's the concrete use case? Same codebase, same query across multiple sessions?

if there's enough demand and the implementation stays simple, I won't block a PR. Open questions if it goes ahead:

• global vs per-repo: less and nvim do global, JetBrains does per-project. Global is simpler, but per-repo is probably more useful (history tied to the codebase you're working on).
• opt-out: search queries can carry sensitive substrings, so a disable knob is required. The less convention is LESSHISTFILE=-; I'd mirror with REVDIFF_SEARCH_HISTORY=- and a config key.
• storage: flat file ~/.config/revdiff/searchhst, one query per line, 50-entry cap (same as feat: in-session search history recall #171).
• default on or off: less defaults on. Given the privacy bar, off-by-default is defensible too.

[amakrushin]

Thanks.

I am a new user of revdiff, and not planning to submit the PR in near future.

Thanks for the in memory search history.