Fits kernel notes / unresolved issues
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Extraneous env variables - put in fkinit

    ENV_DEFIMTYPE   "imtype"
    ENV_FITSCACHE   "fitscache"


Rename

    minhdrlns


Cache

    hard upper limit - is this a restriction?
    convert from common to dynamic descriptor
    referenced:  open delete rename rfits updhdr

Extensions
    should not use imtype to set extension (this is copied from STF which
    also has the same problem)

Defaults / ksection / fkinit
    should overwrite be allowed in fkinit? (fxfopen)

check on file clobber


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Extension, default image type

imtype
    The purpose of imtype is to control the types of images automatically
    created by the system if no image extension is specified.

    new image - determines default image type
    new copy  - determines default image type if noinherit 
    no extn   - up to kernel whether this is legal

    imtype = [(oif|fxf|plf|qpf|stf) | <any-valid-extn>] [[no]inherit]

    save format codes ("oif" etc) in driver descriptors
    extensions are mapped to drivers using imextn


imextn
    map file extensions to image type (kernel)
    default extension for new images of a given type

    imextn = "oif:imh stf:hhh,??h fits:,fits,fit

    or possibly imextn = "imh:oif hhh,??h:stf fits,fit:fit

    kernels:	oif fxf plf qpf stf

	     iki_extninit (imtype, def_imtype, imextn, def_imextn)
	    iki_validextn (kernel, extn)
     status = iki_getextn (kernel, index, extn, maxch)

    Initialize extension processing stuff at iki_init time - only once when
    the process starts up.

    nextn
    { kernel extn patbuf }
    sbuf, sbufused
    defimtype
    inherit

IKI - add kernel arg to:
    access
    copy
    delete
    open
    rename