git-interpret-trailers(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CONFIGURATION VARIABLES | EXAMPLES | SEE ALSO | GIT | COLOPHON

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

NAME         top

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

SYNOPSIS         top

       git interpret-trailers [--in-place] [--trim-empty]
                               [(--trailer (<key>|<keyAlias>)[(=|:)<value>])...]
                               [--parse] [<file>...]

DESCRIPTION         top

       Add or parse trailer lines that look similar to RFC 822 e-mail
       headers, at the end of the otherwise free-form part of a commit
       message. For example, in the following commit message

           subject

           Lorem ipsum dolor sit amet, consectetur adipiscing elit.

           Signed-off-by: Alice <[email protected]>
           Signed-off-by: Bob <[email protected]>

       the last two lines starting with "Signed-off-by" are trailers.

       This command reads 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
       coming from the input, without influencing them with any command
       line options or configuration variables.

       Otherwise, this command applies trailer.* configuration variables
       (which could potentially add new trailers, as well as reposition
       them), as well as any command line arguments that can override
       configuration variables (such as --trailer=... which could also
       add new trailers), to each input file. The result is emitted on
       the standard output.

       This command can also operate on the output of
       git-format-patch(1), which is more elaborate than a plain commit
       message. Namely, such output includes a commit message (as
       above), a "---" divider line, and a patch part. For these inputs,
       the divider and patch parts are not modified by this command and
       are emitted as is on the output, unless --no-divider is
       specified.

       Some configuration variables control the way the --trailer
       arguments 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 <key>=<value> or <key>:<value> argument given using
       --trailer will be appended after the existing trailers only if
       the last trailer has a different (<key>, <value>) pair (or if
       there is no existing trailer). The <key> and <value> parts will
       be trimmed to remove starting and trailing whitespace, and the
       resulting trimmed <key> and <value> will appear in the output
       like this:

           key: value

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

       For convenience, a <keyAlias> can be configured to make using
       --trailer 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 at the end of the input. A blank line will be
       added before the new trailer if there isn’t one already.

       Existing trailers are extracted from the input 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 input or be the last 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 <key>, but any number of regular space and tab
       characters are allowed 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:

           key: This is a very long value, with spaces and
             newlines in it.

       Note that trailers do not follow (nor are they intended to
       follow) many of the rules for RFC 822 headers. For example they
       do not follow the encoding rule.

OPTIONS         top

       --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 output. This
           applies to existing trailers as well as new trailers.

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

       --where <placement>, --no-where
           Specify where all new trailers will be added. A setting
           provided with --where overrides the trailer.where and any
           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 variables are no longer
           overridden. Possible placements 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 <key> in the input. A
           setting provided with --if-exists overrides the
           trailer.ifExists and any 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 variables
           are no longer overridden. 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 <key> in the input. A setting provided
           with --if-missing overrides the trailer.ifMissing and any
           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
           configuration variables are no longer overridden. 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 applying trailer.*  configuration
           variables.

       --unfold
           If a trailer has a value that runs over multiple lines (aka
           "folded"), reformat the value into a single line.

       --parse
           A convenience alias for --only-trailers --only-input
           --unfold. This makes it easier to only see the trailers
           coming from the input without influencing them with any
           command line options or configuration variables, while also
           making the output machine-friendly with --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         top

       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 <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: <key>% <value> (one
           percent sign and one space will appear between the key 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 <key>.

           If it is before, then each new trailer will appear just
           before the 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 <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 (<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 (<key>, <value>) pair is already in the
           input.

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

           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 <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 <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
           <key> in the input.

           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.<keyAlias>.key
           Defines a <keyAlias> for the <key>. The <keyAlias> must be a
           prefix (case does not matter) of the <key>. For example, in
           git config trailer.ack.key "Acked-by" the "Acked-by" is the
           <key> and the "ack" is the <keyAlias>. This configuration
           allows the shorter --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.<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 <keyAlias>.

       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 <keyAlias>.

       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 <keyAlias>.

       trailer.<keyAlias>.command
           Deprecated in favor of trailer.<keyAlias>.cmd. 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.

           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.<keyAlias>.cmd and
           trailer.<keyAlias>.command are given for the same <keyAlias>,
           trailer.<keyAlias>.cmd is used and trailer.<keyAlias>.command
           is ignored.

       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 <keyAlias>, and then 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 <keyAlias>, the behavior is as if a
           special --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 <keyAlias>=<value> arguments are also
           passed on the command line, the command is called again once
           for each 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 <keyAlias>=<value> argument.

EXAMPLES         top

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

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

               body text
               $ git interpret-trailers --trailer 'sign: Alice <[email protected]>' --trailer 'sign: Bob <[email protected]>' <msg.txt
               subject

               body text

               Signed-off-by: Alice <[email protected]>
               Signed-off-by: Bob <[email protected]>

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

               $ cat msg.txt
               subject

               body text

               Signed-off-by: Bob <[email protected]>
               $ git interpret-trailers --trailer 'Acked-by: Alice <[email protected]>' --in-place msg.txt
               $ cat msg.txt
               subject

               body text

               Signed-off-by: Bob <[email protected]>
               Acked-by: Alice <[email protected]>

       •   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 <[email protected]>' --trailer 'Reviewed-by: Bob <[email protected]>' 0001-foo.patch >0001-bar.patch

       •   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:

               $ cat msg1.txt
               subject

               body text
               $ git config trailer.sign.key "Signed-off-by: "
               $ git config trailer.sign.ifmissing add
               $ git config trailer.sign.ifexists doNothing
               $ git config trailer.sign.cmd 'echo "$(git config user.name) <$(git config user.email)>"'
               $ git interpret-trailers --trailer sign <msg1.txt
               subject

               body text

               Signed-off-by: Bob <[email protected]>
               $ cat msg2.txt
               subject

               body text

               Signed-off-by: Alice <[email protected]>
               $ git interpret-trailers --trailer sign <msg2.txt
               subject

               body text

               Signed-off-by: Alice <[email protected]>

       •   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

       •   Configure a help trailer with a cmd use a script
           glog-find-author which search specified author identity from
           git log in git repository and show how it works:

               $ cat ~/bin/glog-find-author
               #!/bin/sh
               test -n "$1" && git log --author="$1" --pretty="%an <%ae>" -1 || true
               $ cat msg.txt
               subject

               body text
               $ git config trailer.help.key "Helped-by: "
               $ git config trailer.help.ifExists "addIfDifferentNeighbor"
               $ git config trailer.help.cmd "~/bin/glog-find-author"
               $ git interpret-trailers --trailer="help:Junio" --trailer="help:Couder" <msg.txt
               subject

               body text

               Helped-by: Junio C Hamano <[email protected]>
               Helped-by: Christian Couder <[email protected]>

       •   Configure a ref trailer with a cmd use a script glog-grep to
           grep last relevant commit from git log in the git repository
           and show how it works:

               $ cat ~/bin/glog-grep
               #!/bin/sh
               test -n "$1" && git log --grep "$1" --pretty=reference -1 || true
               $ cat msg.txt
               subject

               body text
               $ git config trailer.ref.key "Reference-to: "
               $ git config trailer.ref.ifExists "replace"
               $ git config trailer.ref.cmd "~/bin/glog-grep"
               $ git interpret-trailers --trailer="ref:Add copyright notices." <msg.txt
               subject

               body text

               Reference-to: 8bc9a0c769 (Add copyright notices., 2005-04-07)

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

               $ cat msg.txt
               subject

               body text

               see: HEAD~2
               $ cat ~/bin/glog-ref
               #!/bin/sh
               git log -1 --oneline --format="%h (%s)" --abbrev-commit --abbrev=14
               $ git config trailer.see.key "See-also: "
               $ git config trailer.see.ifExists "replace"
               $ git config trailer.see.ifMissing "doNothing"
               $ git config trailer.see.cmd "glog-ref"
               $ git interpret-trailers --trailer=see <msg.txt
               subject

               body text

               See-also: fe3187489d69c4 (subject of related commit)

       •   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:

               $ cat temp.txt
               ***subject***

               ***message***

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

SEE ALSO         top

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

GIT         top

       Part of the git(1) suite

COLOPHON         top

       This page is part of the git (Git distributed version control
       system) project.  Information about the project can be found at
       ⟨http:https://git-scm.com/⟩.  If you have a bug report for this manual
       page, see ⟨http:https://git-scm.com/community⟩.  This page was obtained
       from the project's upstream Git repository
       ⟨https://github.com/git/git.git⟩ on 2023-12-22.  (At that time,
       the date of the most recent commit that was found in the
       repository was 2023-12-20.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       [email protected]

Git 2.43.0.174.g055bb6         2023-12-20      GIT-INTERPRET-TRAILERS(1)

Pages that refer to this page: git(1)git-commit(1)git-diff-tree(1)git-for-each-ref(1)git-log(1)git-rev-list(1)git-shortlog(1)git-show(1)