Is there a git repository service that is accepting bug fixes for Magento CE 1.9?

The restriction is that the conditions must match, otherwise the skipping of unused branches does not work as expected.

There are several methods. The following exampe uses \ifx and compares the constructed conditional with \iftrue. Because we have already \ifx, the latter is also masked by \csname:

\documentclass{article}
\begin{document}
\newif\ifconditionA
\conditionAtrue

\def\test#1#2{%
  \ifcase#2
    Case 0
  \or
    \expandafter
    \ifx\csname ifcondition#1\expandafter\endcsname
        \csname iftrue\endcsname
      Case 1, A: true
    \fi
  \fi
}

\test{A}{0}
\test{A}{1}

\end{document}

If you want to have something clearer to use inside macro \test, then the magic can be hidden in a macro, e.g.:

\documentclass{article}
\begin{document}
\newif\ifconditionA
\conditionAtrue

\newcommand*{\getcondition}[1]{%
  T\expandafter
  \ifx\csname ifcondition#1\endcsname\iftrue
    \expandafter T%
  \else
    \expandafter F%
  \fi
}

\def\test#1#2{%
  \ifcase#2
    Case 0%
  \or
    \if\getcondition{#1}%
      Case 1, #1: true%
    \else
      Case 1, #1: false%
    \fi
  \else
    Other case%
  \fi
}

[\test{A}{0}]
[\test{A}{1}]
[\test{B}{0}]
[\test{B}{1}]
[\test{A}{2}]

\end{document}

This is equivalent to computing the Wronskian of $J_0$ and $Y_0$, since $J'_0 = -J_1$ and $Y'_0 = -Y_1$. $$ W(x) = \begin{vmatrix} J_0 & Y_0 \\\ J'_0 & Y'_0 \end{vmatrix} = \begin{vmatrix} J_0 & Y_0 \\\ -J_1 & -Y_1 \end{vmatrix} = J_1 Y_0 - J_0 Y_1. $$ But the zeroth-order Bessel equation is: $$ \frac{d^2y}{dx^2} + \frac{1}{x}\frac{dy}{dx} + y = 0. $$ By Abel's formula, $W(a) = \frac{W(1)}{a}$. You now have to compute any value of $W$.