bisect: explain the rationale behind 125

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/git-bisect.txt b/Documentation/git-bisect.txt
index c39d957c3a3a432f5e685d44066c145f03b96365..1701e42e4aa87fe6beb78c38201ae35adf1d68dd 100644 (file)
--- a/Documentation/git-bisect.txt
+++ b/Documentation/git-bisect.txt
@@ -241,7 +241,12 @@ exit(3) manual page), as the value is chopped with "& 0377".
 
 The special exit code 125 should be used when the current source code
 cannot be tested. If the script exits with this code, the current
 
 The special exit code 125 should be used when the current source code
 cannot be tested. If the script exits with this code, the current

-revision will be skipped (see `git bisect skip` above).
+revision will be skipped (see `git bisect skip` above). 125 was chosen
+as the highest sensible value to use for this purpose, because 126 and 127
+are used by POSIX shells to signal specific error status (127 is for
+command not found, 126 is for command found but not executable---these
+details do not matter, as they are normal errors in the script, as far as
+"bisect run" is concerned).

 
 You may often find that during a bisect session you want to have
 temporary modifications (e.g. s/#define DEBUG 0/#define DEBUG 1/ in a
 
 You may often find that during a bisect session you want to have
 temporary modifications (e.g. s/#define DEBUG 0/#define DEBUG 1/ in a