docs: correct descript of trailer.<token>.command

In the original documentation of `trailer.<token>.command`,
some descriptions are easily misunderstood. So let's modify
it to increase its readability.

In addition, clarify that `$ARG` in command can only be
replaced once.

Signed-off-by: ZheNing Hu <adlternative@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
pull/1018/head
ZheNing Hu 2 years ago committed by Junio C Hamano
parent 2daae3d1d1
commit 57dcb6575b
  1. 37
      Documentation/git-interpret-trailers.txt

@ -232,25 +232,30 @@ trailer.<token>.ifmissing::
that option for trailers with the specified <token>.
trailer.<token>.command::
This option can be used to specify a shell command that will
be called to automatically add or modify a trailer with the
specified <token>.
This option can be used to specify a shell command that will be called:
once to automatically add a trailer with the specified <token>, and then
each time a '--trailer <token>=<value>' argument to modify the <value> of
the trailer that this option would produce.
+
When this option is specified, the behavior is as if a special
'<token>=<value>' argument were added at the beginning of the command
line, where <value> is taken to be the standard output of the
specified command with any leading and trailing whitespace trimmed
off.
When the specified command is first called to add a trailer
with the specified <token>, the behavior is as if a special
'--trailer <token>=<value>' argument was added at the beginning
of the "git interpret-trailers" command, where <value>
is taken to be the standard output of the command with any
leading and trailing whitespace trimmed off.
+
If the command contains the `$ARG` string, this string will be
replaced with the <value> part of an existing trailer with the same
<token>, if any, before the command is launched.
If some '--trailer <token>=<value>' arguments are also passed
on the command line, the command is called again once for each
of these arguments with the same <token>. And the <value> part
of these arguments, if any, will be used to replace the first
occurrence of substring `$ARG` in the command. This way the
command can produce a <value> computed from the <value> passed
in the '--trailer <token>=<value>' argument.
+
If some '<token>=<value>' arguments are also passed on the command
line, when a 'trailer.<token>.command' is configured, the command will
also be executed for each of these arguments. And the <value> part of
these arguments, if any, will be used to replace the `$ARG` string in
the command.
For consistency, the first occurrence of substring `$ARG` is
also replaced, this time with the empty string, in the command
when the command is first called to add a trailer with the
specified <token>.
EXAMPLES
--------

Loading…
Cancel
Save