git-interpret-trailers

GIT-INTERPRET-TRAI(1)             Git Manual             GIT-INTERPRET-TRAI(1)

NAME
       git-interpret-trailers - Add or parse structured information in commit
       messages

SYNOPSIS
       git interpret-trailers [<options>] [(--trailer <token>[(=|:)<value>])...] [<file>...]
       git interpret-trailers [<options>] [--parse] [<file>...]

DESCRIPTION
       Help parsing or adding trailers lines, that look similar to RFC 822
       e-mail headers, at the end of the otherwise free-form part of a commit
       message.

       This command reads some patches or commit messages from either the
       <file> arguments or the standard input if no <file> is specified. If
       --parse is specified, the output consists of the parsed trailers.

       Otherwise, this command applies the arguments passed using the
       --trailer option, if any, to the commit message part of each input
       file. The result is emitted on the standard output.

       Some configuration variables control the way the --trailer arguments
       are applied to each commit message and the way any existing trailer in
       the commit message is changed. They also make it possible to
       automatically add some trailers.

       By default, a <token>=<value> or <token>:<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 is no
       existing trailer). The <token> and <value> parts will be trimmed to
       remove starting and trailing whitespace, and the resulting trimmed
       <token> and <value> will appear in the message like this:

           token: value

       This means that the trimmed <token> and <value> will be separated by ':
       ' (one colon followed by one space).

       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
       after the commit message part of the output, and, if there is no line
       with only spaces at the end of the commit message part, one blank line
       will be added before the new trailer.

       Existing trailers are extracted from the input message by looking for a
       group of one or more lines that (i) is all trailers, or (ii) contains
       at least one Git-generated or user-configured trailer and consists of
       at least 25% trailers. The group must be preceded by one or more empty
       (or whitespace-only) lines. The group must either be at the end of the
       message or be the last non-whitespace lines before a line that starts
       with --- (followed by a space or the end of the line). Such three minus
       signs start the patch part of the message. See also --no-divider below.

       When reading trailers, there can be whitespaces after the token, the
       separator and the value. There can also be whitespaces inside the token
       and the value. The value may be split over multiple lines with each
       subsequent line starting with whitespace, like the "folding" in RFC
       822.

       Note that trailers do not follow and are not intended to follow many
       rules for RFC 822 headers. For example they do not follow the encoding
       rules and probably many other rules.

OPTIONS
       --in-place
           Edit the files in place.

       --trim-empty
           If the <value> part of any trailer contains only whitespace, the
           whole trailer will be removed from the resulting message. This
           applies to existing trailers as well as new trailers.

       --trailer <token>[(=|:)<value>]
           Specify a (<token>, <value>) pair that should be applied as a
           trailer to the input messages. See the description of this command.

       --where <placement>, --no-where
           Specify where all new trailers will be added. A setting provided
           with --where overrides all configuration variables and applies to
           all --trailer options until the next occurrence of --where or
           --no-where. Possible values are after, before, end or start.

       --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 message. A setting
           provided with --if-exists overrides all configuration variables and
           applies to all --trailer options until the next occurrence of
           --if-exists or --no-if-exists. Possible actions are addIfDifferent,
           addIfDifferentNeighbor, add, replace and doNothing.

       --if-missing <action>, --no-if-missing
           Specify what action will be performed when there is no other
           trailer with the same <token> in the message. A setting provided
           with --if-missing overrides all configuration variables and applies
           to all --trailer options until the next occurrence of --if-missing
           or --no-if-missing. Possible actions are doNothing or add.

       --only-trailers
           Output only the trailers, not any other parts of the input.

       --only-input
           Output only trailers that exist in the input; do not add any from
           the command-line or by following configured trailer.*  rules.

       --unfold
           Remove any whitespace-continuation in trailers, so that each
           trailer appears on a line by itself with its full content.

       --parse
           A convenience alias for --only-trailers --only-input --unfold.

       --no-divider
           Do not treat --- as the end of the commit message. Use this when
           you know your input contains just the commit message itself (and
           not an email or the output of git format-patch).

CONFIGURATION VARIABLES
       trailer.separators
           This option tells which characters are recognized as trailer
           separators. By default only : is recognized as a trailer separator,
           except that = is always accepted on the command line for
           compatibility with other git commands.

           The first character given by this option will be the default
           character 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 %, = 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 the token and the value).

       trailer.where
           This option tells where a new trailer will be added.

           This can be end, which is the default, start, after or before.

           If it is end, then each new trailer will appear at the end of the
           existing trailers.

           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>.

           If it is before, then each new trailer will appear just before the
           first trailer with the same <token>.

       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 message.

           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 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 message.

           With add, a new trailer will be added, even if some trailers with
           the same (<token>, <value>) pair are already in the message.

           With replace, an existing trailer with the same <token> 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 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
           message.

       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 message.

           The valid values for this option are: add (this is the default) and
           doNothing.

           With add, a new trailer will be added.

           With doNothing, nothing will be done.

       trailer.<token>.key
           This key will be used instead of <token> in the trailer. At the end
           of this 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, then the key will be used instead of both
           the <token> and the default separator when adding the trailer.

       trailer.<token>.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>.

       trailer.<token>.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>.

       trailer.<token>.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>.

       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>.

           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.

           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 <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.

EXAMPLES
       o   Configure a sign trailer with a Signed-off-by key, and then add two
           of these trailers to a message:

               $ git config trailer.sign.key "Signed-off-by"
               $ cat msg.txt
               subject

               message
               $ cat msg.txt | git interpret-trailers --trailer 'sign: Alice <alice@example.com>' --trailer 'sign: Bob <bob@example.com>'
               subject

               message

               Signed-off-by: Alice <alice@example.com>
               Signed-off-by: Bob <bob@example.com>

       o   Use the --in-place option to edit a message file in place:

               $ cat msg.txt
               subject

               message

               Signed-off-by: Bob <bob@example.com>
               $ git interpret-trailers --trailer 'Acked-by: Alice <alice@example.com>' --in-place msg.txt
               $ cat msg.txt
               subject

               message

               Signed-off-by: Bob <bob@example.com>
               Acked-by: Alice <alice@example.com>

       o   Extract the last commit as a patch, and add a Cc and a Reviewed-by
           trailer to it:

               $ git format-patch -1
               0001-foo.patch
               $ git interpret-trailers --trailer 'Cc: Alice <alice@example.com>' --trailer 'Reviewed-by: Bob <bob@example.com>' 0001-foo.patch >0001-bar.patch

       o   Configure a sign trailer with a command to automatically add a
           'Signed-off-by: ' with the author information only if there is no
           'Signed-off-by: ' already, and show how it works:

               $ git config trailer.sign.key "Signed-off-by: "
               $ git config trailer.sign.ifmissing add
               $ git config trailer.sign.ifexists doNothing
               $ git config trailer.sign.command 'echo "$(git config user.name) <$(git config user.email)>"'
               $ git interpret-trailers <<EOF
               > EOF

               Signed-off-by: Bob <bob@example.com>
               $ git interpret-trailers <<EOF
               > Signed-off-by: Alice <alice@example.com>
               > EOF

               Signed-off-by: Alice <alice@example.com>

       o   Configure a fix trailer with a key that contains a # and no space
           after this character, and show how it works:

               $ git config trailer.separators ":#"
               $ git config trailer.fix.key "Fix #"
               $ echo "subject" | git interpret-trailers --trailer fix=42
               subject

               Fix #42

       o   Configure a see trailer with a command to show the subject of a
           commit that is related, and show how it works:

               $ git config trailer.see.key "See-also: "
               $ git config trailer.see.ifExists "replace"
               $ git config trailer.see.ifMissing "doNothing"
               $ git config trailer.see.command "git log -1 --oneline --format=\"%h (%s)\" --abbrev-commit --abbrev=14 \$ARG"
               $ git interpret-trailers <<EOF
               > subject
               >
               > message
               >
               > see: HEAD~2
               > EOF
               subject

               message

               See-also: fe3187489d69c4 (subject of related commit)

       o   Configure a commit template with some trailers with empty values
           (using sed to show and keep the trailing spaces at the end of the
           trailers), then configure a commit-msg hook that uses git
           interpret-trailers to remove trailers with empty values and to add
           a git-version trailer:

               $ sed -e 's/ Z$/ /' >commit_template.txt <<EOF
               > ***subject***
               >
               > ***message***
               >
               > Fixes: Z
               > Cc: Z
               > Reviewed-by: Z
               > Signed-off-by: Z
               > EOF
               $ git config commit.template commit_template.txt
               $ cat >.git/hooks/commit-msg <<EOF
               > #!/bin/sh
               > git interpret-trailers --trim-empty --trailer "git-version: \$(git describe)" "\$1" > "\$1.new"
               > mv "\$1.new" "\$1"
               > EOF
               $ chmod +x .git/hooks/commit-msg

SEE ALSO
       git-commit(1), git-format-patch(1), git-config(1)

GIT
       Part of the git(1) suite

Git 2.25.1                        04/26/2023             GIT-INTERPRET-TRAI(1)