PL4 drops too much in \DeclareFontShape

[FrankMittelbach]

Brief outline of the bug

PL4 was introduced to correct \DeclareFontShape declarations that incorrectly used something like mc when it should be c, according to the NFSS rules. Unfortunately the approach to drop a surplus "m" from the series unconditionally was a bit too overambitious because some .fd files (in particular those made with autoinst) first set up font shapes using long font names in the series, e.g. regular or semibold and then map the NFSS names onto the long names, eg.

\DeclareFontShape{OT1}{EBGaramond-OsF}{semibold}{n}{
      <-> \EBGaramond@@scale EBGaramond-SemiBold-osf-ot1
}{}
\DeclareFontShape{OT1}{EBGaramond-OsF}{sb}{n}{
       <-> ssub * EBGaramond-OsF/semibold/n
}{} 

Now when dropping one m from the series that results in the first one being equivalent to semibold and so the second misses its mark.

Minimal example showing the bug

\RequirePackage{latexbug}       % <--should be always the first line (see CONTRIBUTING)!
 \documentclass{article}

\begin{document}

\fontfamily{EBGaramond-OsF}\fontseries{semibold}\selectfont Test

\fontseries{sb}\selectfont Test

\end{document}

Log file

PL4-issue2.log

[FrankMittelbach]

gone to CTAN as PL5