rebase -i: clarify in-editor documentation of "exec"

The hints in the current "instruction sheet" template look like so: # Rebase 3f14246..a1d7e01 onto 3f14246 # # Commands: # p, pick = use commit # r, reword = use commit, but edit the commit message # e, edit = use commit, but stop for amending # s, squash = use commit, but meld into previous commit # f, fixup = like "squash", but discard this commit's log message # x <cmd>, exec <cmd> = Run a shell command <cmd>, and stop if it fails # # If you remove a line here THAT COMMIT WILL BE LOST. # However, if you remove everything, the rebase will be aborted. # This does not make it clear that the format of each line is <insn> <commit id> <explanatory text that will be printed> but the reader will probably infer that from the automatically generated pick examples above it. What about the "exec" instruction? By analogy, I might imagine that the format of that line is "exec <command> <explanatory text>", and the "x <cmd>" hint does not address that question (at first I read it as taking an argument <cmd> that is the name of a shell). Meanwhile, the mention of <cmd> makes the hints harder to scan as a table. So remove the <cmd> and add some words to remind the reader that "exec" runs a command named by the rest of the line. To make room, it is left to the manpage to explain that that command is run using $SHELL and that nonzero status from that command will pause the rebase. Wording from Junio. Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>