The option `case-sensitive = false` invalidates `use-id-as-short = true`

Hi there @cgnieder, thanks for the package, it is great! I currently have a difficulty with the combination of the case-sensitive and use-id-as-short options.

I use the case-sensitive = false option to ensure acronyms will work in chapter headings, \chaptermark calls and the like. However, to my understanding, this currently invalidates the use of use-id-as-short = true, since using the setup below forces all short-versions of acronyms in the text to assume lower-case format.

\acsetup{
    case-sensitive = false,     % Ignore case in IDs (needed for \chaptermark)
    use-id-as-short = true,     % Use ID as short version, unless specified
}

\DeclareAcronym{HDMI}{long = High Definition...}

\ac{HDMI}

prints High Definition... (hdmi) instead of High Definition... (HDMI)

I understand that I could forcefully provide \DeclareAcronym{HDMI}{short=HDMI, long = High Definition...}, but this is what use-id-as-short should avoid.

TLDR: is there a way of ensuring that calls of \ac-like commands are case-insensitive when case-sensitive = false, but also print the short versions as defined when use-id-as-short = true? In the example above, I expect:

\DeclareAcronym{HdMi}{long = High Definition...}
\ac{hdmi}

to print High Definition... (HdMi) and not High Definition... (hdmi)

cgnieder / acro

The option `case-sensitive = false` invalidates `use-id-as-short = true` #275