[Rpm-maint] [rpm-software-management/rpm] RFE: Handle disttag (#589)

[Ivan Zakharyaschev]

On Sat, 10 Nov 2018, Jeff Johnson wrote:

> @imz: it's the EVR string in a separate tag, not the NEVR or NEVRA (or variants including DistTag) identifiers where the parsing complexities (including missing values) are hidden.
> 
> The parsing rules (which you mentioned) that splits N from the rest (in an explicit NEVRDA) string is basically

Thanks for writing them out explicitly!

I haven't understood how a command like

    rpm --query -- -release

or

    rpm --query -- -release:disttag

is relevant for this discussion. Does anyone call `rpm --query` without a 
name in the argument?

> The last dash is the separator between V-R, the 2nd to last dash is the separator between N and the rest. None of V or R or D or A may include a dash.
> 
> Arch parsing can be handled with a period, followed by key words like "i686" or "x86_64".
> 
> What remains is EVRD which must be parsed unambiguously whatever separator characters are used, including unspecified or missing values.
> 
> Epoch is a digit string up to the first colon, D (as in the PCRE) is whatever follows the last colon (and colon is a forbidden character in the D string).
> 
> The PCRE breaks the EVRD string into substrings assigned to known match indices while also handling missing/unspecified matches.


-- 
Best regards,
Ivan


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