Comment 1 for bug 1517956

Example command:

xdg-settings set default-web-browser chromium-browser.desktop

In searching the desktop file for suitability, it scans for all lines that begin "Exec", and takes the result and packs it into a variable.

If there is exactly one Exec line, this takes out a command name to test for existence, but when more than one matches, the program name is captured as "firstexecprog\nsecondexecprog\nthirdexecprog", and "which" doesn't know how to look up a program like that and the subsequent tests fail.

Output with sh's "-x" option on:

+ grep -E ^Exec(\[[^]=]*])?= /usr/share//applications/chromium-browser.desktop
+ command=chromium-browser
chromium-browser
chromium-browser
chromium-browser
+ which chromium-browser
chromium-browser
chromium-browser
chromium-browser
+ command=
+ readlink -f
+ return
+ binary=
+ [ ]
+ exit_failure_file_missing
+ [ 0 -gt 0 ]

In desktop_file_to_binary and binary_to_desktop_file functions, it makes false assumptions how many times grep may match. Those should treat each Exec match separately.