[PATCH v8 1/2] [GSOC] docs: correct descript of trailer.<token>.command

["ZheNing Hu via GitGitGadget" <gitgitgadget@gmail.com>]

From: ZheNing Hu <adlternative@gmail.com>

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 `$ARG` in command can only be
replaced once since `$ARG` is text replacement.

Signed-off-by: ZheNing Hu <adlternative@gmail.com>
---
 Documentation/git-interpret-trailers.txt | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/Documentation/git-interpret-trailers.txt b/Documentation/git-interpret-trailers.txt
index 96ec6499f001..3e5aa3a65ae9 100644
--- a/Documentation/git-interpret-trailers.txt
+++ b/Documentation/git-interpret-trailers.txt
@@ -237,20 +237,20 @@ trailer.<token>.command::
 	specified <token>.
 +
 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.
+'--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 specified command with any leading and trailing
+whitespace trimmed off.
 +
-If the command contains the `$ARG` string, this string will be
-replaced with the <value> part of an existing trailer with the same
-<token>, if any, before the command is launched.
+The first occurrence of substring `$ARG` will be replaced with the
+<value> part of an existing trailer with the same <token>, if any,
+before the command is launched.
 +
 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 `$ARG` string in
-the command.
+line, when a 'trailer.<token>.command' is configured, the command is run
+once for each these arguments with the same <token>. And the <value>
+part of these arguments, if any, will be used to replace the first `$ARG`
+string in the command.
 
 EXAMPLES
 --------
-- 
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