trailer doc: <token> is a <key> or <keyAlias>, not both

The `--trailer` option takes a "<token>=<value>" argument, for example

    --trailer "Acked-by=Bob"

And in this exampple it is understood that "Acked-by" is the <token>.
However, the user can use a shorter "ack" string by defining
configuration like

    git config trailer.ack.key "Acked-by"

However, in the docs we define the above configuration as

    trailer.<token>.key

so the <token> can mean either the longer "Acked-by" or the shorter
"ack".

Separate the two meanings of <token> into <key> and <keyAlias>, and
update the configuration syntax to say "trailer.<keyAlias>.key".

Signed-off-by: Linus Arver <linusa@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-interpret-trailers.txt

@@ -9,7 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'git interpret-trailers' [--in-place] [--trim-empty]
-			[(--trailer <token>[(=|:)<value>])...]
+			[(--trailer (<key>|<keyAlias>)[(=|:)<value>])...]
 			[--parse] [<file>...]
 
 DESCRIPTION
@@ -53,22 +53,32 @@ are applied to each input and the way any existing trailer in
 the input is changed. They also make it possible to
 automatically add some trailers.
 
-By default, a '<token>=<value>' or '<token>:<value>' argument given
+By default, a '<key>=<value>' or '<key>:<value>' argument given
 using `--trailer` will be appended after the existing trailers only if
-the last trailer has a different (<token>, <value>) pair (or if there
+the last trailer has a different (<key>, <value>) pair (or if there
-is no existing trailer). The <token> and <value> parts will be trimmed
+is no existing trailer). The <key> and <value> parts will be trimmed
 to remove starting and trailing whitespace, and the resulting trimmed
-<token> and <value> will appear in the output like this:
+<key> and <value> will appear in the output like this:
 
 ------------------------------------------------
-token: value
+key: value
 ------------------------------------------------
 
-This means that the trimmed <token> and <value> will be separated by
+This means that the trimmed <key> and <value> will be separated by
-`': '` (one colon followed by one space). For convenience, the <token> can be a
+`': '` (one colon followed by one space).
-shortened string key (e.g., "sign") instead of the full string which should
+
-appear before the separator on the output (e.g., "Signed-off-by"). This can be
+For convenience, a <keyAlias> can be configured to make using `--trailer`
-configured using the 'trailer.<token>.key' configuration variable.
+shorter to type on the command line. This can be configured using the
+'trailer.<keyAlias>.key' configuration variable. The <keyAlias> must be a prefix
+of the full <key> string, although case sensitivity does not matter. For
+example, if you have
+
+------------------------------------------------
+trailer.sign.key "Signed-off-by: "
+------------------------------------------------
+
+in your configuration, you only need to specify `--trailer="sign: foo"`
+on the command line instead of `--trailer="Signed-off-by: foo"`.
 
 By default the new trailer will appear at the end of all the existing
 trailers. If there is no existing trailer, the new trailer will appear
@@ -85,14 +95,14 @@ non-whitespace lines before a line that starts with '---' (followed by a
 space or the end of the line).
 
 When reading trailers, there can be no whitespace before or inside the
-<token>, but any number of regular space and tab characters are allowed
+<key>, but any number of regular space and tab characters are allowed
-between the <token> and the separator. There can be whitespaces before,
+between the <key> and the separator. There can be whitespaces before,
 inside or after the <value>. The <value> may be split over multiple lines
 with each subsequent line starting with at least one whitespace, like
 the "folding" in RFC 822. Example:
 
 ------------------------------------------------
-token: This is a very long value, with spaces and
+key: This is a very long value, with spaces and
   newlines in it.
 ------------------------------------------------
 
@@ -109,8 +119,8 @@ OPTIONS
 	the whole trailer will be removed from the output.
 	This applies to existing trailers as well as new trailers.
 
---trailer <token>[(=|:)<value>]::
+--trailer <key>[(=|:)<value>]::
-	Specify a (<token>, <value>) pair that should be applied as a
+	Specify a (<key>, <value>) pair that should be applied as a
 	trailer to the inputs. See the description of this
 	command.
 
@@ -118,7 +128,7 @@ OPTIONS
 --no-where::
 	Specify where all new trailers will be added.  A setting
 	provided with '--where' overrides the `trailer.where` and any
-	applicable `trailer.<token>.where` configuration variables
+	applicable `trailer.<keyAlias>.where` configuration variables
 	and applies to all '--trailer' options until the next occurrence of
 	'--where' or '--no-where'. Upon encountering '--no-where', clear the
 	effect of any previous use of '--where', such that the relevant configuration
@@ -128,9 +138,9 @@ OPTIONS
 --if-exists <action>::
 --no-if-exists::
 	Specify what action will be performed when there is already at
-	least one trailer with the same <token> in the input.  A setting
+	least one trailer with the same <key> in the input.  A setting
 	provided with '--if-exists' overrides the `trailer.ifExists` and any
-	applicable `trailer.<token>.ifExists` configuration variables
+	applicable `trailer.<keyAlias>.ifExists` configuration variables
 	and applies to all '--trailer' options until the next occurrence of
 	'--if-exists' or '--no-if-exists'. Upon encountering '--no-if-exists, clear the
 	effect of any previous use of '--if-exists, such that the relevant configuration
@@ -140,9 +150,9 @@ OPTIONS
 --if-missing <action>::
 --no-if-missing::
 	Specify what action will be performed when there is no other
-	trailer with the same <token> in the input.  A setting
+	trailer with the same <key> in the input.  A setting
 	provided with '--if-missing' overrides the `trailer.ifMissing` and any
-	applicable `trailer.<token>.ifMissing` configuration variables
+	applicable `trailer.<keyAlias>.ifMissing` configuration variables
 	and applies to all '--trailer' options until the next occurrence of
 	'--if-missing' or '--no-if-missing'. Upon encountering '--no-if-missing,
 	clear the effect of any previous use of '--if-missing, such that the relevant
@@ -187,11 +197,11 @@ used when another separator is not specified in the config for this
 trailer.
 +
 For example, if the value for this option is "%=$", then only lines
-using the format '<token><sep><value>' with <sep> containing '%', '='
+using the format '<key><sep><value>' with <sep> containing '%', '='
 or '$' and then spaces will be considered trailers. And '%' will be
 the default separator used, so by default trailers will appear like:
-'<token>% <value>' (one percent sign and one space will appear between
+'<key>% <value>' (one percent sign and one space will appear between
-the token and the value).
+the key and the value).
 
 trailer.where::
 	This option tells where a new trailer will be added.
@@ -205,41 +215,41 @@ If it is `start`, then each new trailer will appear at the start,
 instead of the end, of the existing trailers.
 +
 If it is `after`, then each new trailer will appear just after the
-last trailer with the same <token>.
+last trailer with the same <key>.
 +
 If it is `before`, then each new trailer will appear just before the
-first trailer with the same <token>.
+first trailer with the same <key>.
 
 trailer.ifexists::
 	This option makes it possible to choose what action will be
 	performed when there is already at least one trailer with the
-	same <token> in the input.
+	same <key> in the input.
 +
 The valid values for this option are: `addIfDifferentNeighbor` (this
 is the default), `addIfDifferent`, `add`, `replace` or `doNothing`.
 +
 With `addIfDifferentNeighbor`, a new trailer will be added only if no
-trailer with the same (<token>, <value>) pair is above or below the line
+trailer with the same (<key>, <value>) pair is above or below the line
 where the new trailer will be added.
 +
 With `addIfDifferent`, a new trailer will be added only if no trailer
-with the same (<token>, <value>) pair is already in the input.
+with the same (<key>, <value>) pair is already in the input.
 +
 With `add`, a new trailer will be added, even if some trailers with
-the same (<token>, <value>) pair are already in the input.
+the same (<key>, <value>) pair are already in the input.
 +
-With `replace`, an existing trailer with the same <token> will be
+With `replace`, an existing trailer with the same <key> will be
 deleted and the new trailer will be added. The deleted trailer will be
-the closest one (with the same <token>) to the place where the new one
+the closest one (with the same <key>) to the place where the new one
 will be added.
 +
 With `doNothing`, nothing will be done; that is no new trailer will be
-added if there is already one with the same <token> in the input.
+added if there is already one with the same <key> in the input.
 
 trailer.ifmissing::
 	This option makes it possible to choose what action will be
 	performed when there is not yet any trailer with the same
-	<token> in the input.
+	<key> in the input.
 +
 The valid values for this option are: `add` (this is the default) and
 `doNothing`.
@@ -248,34 +258,40 @@ With `add`, a new trailer will be added.
 +
 With `doNothing`, nothing will be done.
 
-trailer.<token>.key::
+trailer.<keyAlias>.key::
-	This `key` will be used instead of <token> in the trailer. At
+	Defines a <keyAlias> for the <key>. The <keyAlias> must be a
-	the end of this key, a separator can appear and then some
+	prefix (case does not matter) of the <key>. For example, in `git
-	space characters. By default the only valid separator is ':',
+	config trailer.ack.key "Acked-by"` the "Acked-by" is the <key> and
-	but this can be changed using the `trailer.separators` config
+	the "ack" is the <keyAlias>. This configuration allows the shorter
-	variable.
+	`--trailer "ack:..."` invocation on the command line using the "ack"
+	<keyAlias> instead of the longer `--trailer "Acked-by:..."`.
++
+At the end of the <key>, a separator can appear and then some
+space characters. By default the only valid separator is ':',
+but this can be changed using the `trailer.separators` config
+variable.
 +
 If there is a separator in the key, then it overrides the default
 separator when adding the trailer.
 
-trailer.<token>.where::
+trailer.<keyAlias>.where::
 	This option takes the same values as the 'trailer.where'
 	configuration variable and it overrides what is specified by
-	that option for trailers with the specified <token>.
+	that option for trailers with the specified <keyAlias>.
 
-trailer.<token>.ifexists::
+trailer.<keyAlias>.ifexists::
 	This option takes the same values as the 'trailer.ifexists'
 	configuration variable and it overrides what is specified by
-	that option for trailers with the specified <token>.
+	that option for trailers with the specified <keyAlias>.
 
-trailer.<token>.ifmissing::
+trailer.<keyAlias>.ifmissing::
 	This option takes the same values as the 'trailer.ifmissing'
 	configuration variable and it overrides what is specified by
-	that option for trailers with the specified <token>.
+	that option for trailers with the specified <keyAlias>.
 
-trailer.<token>.command::
+trailer.<keyAlias>.command::
-	Deprecated in favor of 'trailer.<token>.cmd'.
+	Deprecated in favor of 'trailer.<keyAlias>.cmd'.
-	This option behaves in the same way as 'trailer.<token>.cmd', except
+	This option behaves in the same way as 'trailer.<keyAlias>.cmd', except
 	that it doesn't pass anything as argument to the specified command.
 	Instead the first occurrence of substring $ARG is replaced by the
 	<value> that would be passed as argument.
@@ -283,29 +299,29 @@ trailer.<token>.command::
 Note that $ARG in the user's command is
 only replaced once and that the original way of replacing $ARG is not safe.
 +
-When both 'trailer.<token>.cmd' and 'trailer.<token>.command' are given
+When both 'trailer.<keyAlias>.cmd' and 'trailer.<keyAlias>.command' are given
-for the same <token>, 'trailer.<token>.cmd' is used and
+for the same <keyAlias>, 'trailer.<keyAlias>.cmd' is used and
-'trailer.<token>.command' is ignored.
+'trailer.<keyAlias>.command' is ignored.
 
-trailer.<token>.cmd::
+trailer.<keyAlias>.cmd::
 	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
+	once to automatically add a trailer with the specified <keyAlias>, and then
-	called each time a '--trailer <token>=<value>' argument is specified to
+	called each time a '--trailer <keyAlias>=<value>' argument is specified to
 	modify the <value> of the trailer that this option would produce.
 +
 When the specified command is first called to add a trailer
-with the specified <token>, the behavior is as if a special
+with the specified <keyAlias>, the behavior is as if a special
-'--trailer <token>=<value>' argument was added at the beginning
+'--trailer <keyAlias>=<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 some '--trailer <token>=<value>' arguments are also passed
+If some '--trailer <keyAlias>=<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 with the same <keyAlias>. And the <value> part
 of these arguments, if any, will be passed to the command as its
 first argument. This way the command can produce a <value> computed
-from the <value> passed in the '--trailer <token>=<value>' argument.
+from the <value> passed in the '--trailer <keyAlias>=<value>' argument.
 
 EXAMPLES
 --------

builtin/interpret-trailers.c

@@ -14,7 +14,7 @@
 
 static const char * const git_interpret_trailers_usage[] = {
 	N_("git interpret-trailers [--in-place] [--trim-empty]\n"
-	   "                       [(--trailer <token>[(=|:)<value>])...]\n"
+	   "                       [(--trailer (<key>|<keyAlias>)[(=|:)<value>])...]\n"
 	   "                       [--parse] [<file>...]"),
 	NULL
 };