# git-interpret-trailers

## NAME



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


## SYNOPSIS



           _git interpret-trailers_ [--in-place] [--trim-empty]
                                   [(--trailer (<key>|<key-alias>)[(=|:)<value>])...]
                                   [--parse] [<file>...]
    


## DESCRIPTION



           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 <alice@example.com>
               Signed-off-by: Bob <bob@example.com>
    
           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 <key-alias> can be configured to make using
           **--trailer** shorter to type on the command line. This can be
           configured using the _trailer. <key-alias>.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



           --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



           Everything below this line in this section is selectively included
           from the git-config(1) documentation. The content is the same as
           what’s found there:
    
           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



           •   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 <alice@example.com>' --trailer 'sign: Bob <bob@example.com>' <msg.txt
                   subject
    
                   body text
    
                   Signed-off-by: Alice <alice@example.com>
                   Signed-off-by: Bob <bob@example.com>
    
           •   Use the **--in-place** option to edit a commit message file in
               place:
    
                   $ cat msg.txt
                   subject
    
                   body text
    
                   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
    
                   body text
    
                   Signed-off-by: Bob <bob@example.com>
                   Acked-by: Alice <alice@example.com>
    
           •   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
    
           •   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 <bob@example.com>
                   $ cat msg2.txt
                   subject
    
                   body text
    
                   Signed-off-by: Alice <alice@example.com>
                   $ git interpret-trailers --trailer sign <msg2.txt
                   subject
    
                   body text
    
                   Signed-off-by: Alice <alice@example.com>
    
           •   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 <gitster@pobox.com>
                   Helped-by: Christian Couder <christian.couder@gmail.com>
    
           •   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
    


## GIT



           Part of the git(1) suite
    


* * *