DH_ASSISTANT(1)

NAME
dh_assistant - tool for supporting debhelper tools and provide introspection

SYNOPSIS
dh_assistant command [additional options]

DESCRIPTION
dh_assistant is a debhelper program that provides introspection into the debhelper stack to assist third-party tools (e.g. linters) or third-party debhelper implementations not using the debhelper script API (e.g., because they are not written in Perl).

COMMANDS
The dh_assistant supports the following commands:

  active-compat-level (AJSON)
Synopsis: dh_assistant active-compat-level

Outputs information about which compat level the package is using.

For packages without valid debhelper compatibility information (whether missing, ambiguous, not supported or simply invalid), this command operates on a "best effort" basis and may abort when error instead of providing data.

The returned JSON dictionary contains the following key-value pairs:

active-compat-level
    The compat level that debhelper will be using. This is the same as DH_COMPAT when present or else declared-compat-level. This can be null when no compat level can be detected.

declared-compat-level
    The compat level that the package declared as its default compat level. This can be null if the package does not declare any compat level at all.

declared-compat-level-source
    Defines how the compat level was declared. This is null (for the same reason as declared-compat-level) or one of:

    debian/compat
        The compatibility level was declared in the single line debian/compat file.

    X-DH-Compat: <C>
        The compatibility was declared in the debian/control via a the X-DH-Compat field. In the output, the C is replaced by the actual compatibility level. A full example value would be:

           X-DH-Compat: 15

    Build-Depends: debhelper-compat (= <C>)
        The compatibility was declared in the debian/control via a build dependency on the debhelper-compat (= <C>) package in the Build-Depends field. In the output, the C is replaced by the actual compatibility level. A full example value would be:

           Build-Depends: debhelper-compat (= 15)

  supported-compat-levels (AJSON, CRFA)
Synopsis: dh_assistant supported-compat-levels

Outputs information about which compat levels, this build of debhelper knows about.

This command accepts no options or arguments.

  which-build-system (AJSON)
Synopsis: dh_assistant which-build-system [build step] [build system options]

Output information about which build system would be used for a particular build step. The build step must be one of configure, build, test, install or clean and must be the first argument after which-build-system when provided. If omitted, it defaults to configure as it is the most reliable step to use auto-detection on in a clean source directory. Note that build steps do not always agree when using auto-detection - particularly if the configure step has not been run.

Additionally, the clean step can also provide "surprising" results for builds that rely on a separate build directory. In such cases, debhelper will return the first build system that uses a separate build directory rather than the one build system that configure would detect. This is generally a cosmetic issue as both build systems are all basically a glorified rm -fr builddir and more precise detection is functionally irrelevant as far as debhelper is concerned.

The option accepts all debhelper build system arguments - i.e., options you can pass to all of the dh_auto_* commands plus (for the install step) the --destdir option. These options affect the output and auto-detection in various ways. Passing -S or --buildsystem overrides the auto-detection (as it does for dh_auto_*) but it still provides introspection into the chosen build system.

Things that are useful to know about the output:

•   The key build-system is the build system that would be used by debhelper for the given step (with the given options, debhelper compat level, environment variables and the given working directory). When -S and --buildsystem are omitted, this is the result of debhelper's auto-detection logic.

    The value is valid as a parameter for the --buildsystem option.

    The special value "none" is used to denote that no build system would be used (that is, a JSON string). This value is not present in --list parameter for the dh_auto_* commands, but since debhelper/12.9 the value is accepted for the --buildsystem option.

    Note that auto-detection is subject to limitations in regards to third-party build systems. While debhelper does support auto-detecting some third-party build systems, they must be installed for the detection to work. If they are not installed, the detection logic silently skips that build system (often resulting in build-system being "none" in the output).

•   The build-directory and buildpath values serve different but related purposes. The build-directory generally mirrors the --builddirectory option where as buildpath is the output directory that debhelper will use. Therefore the former will often be null when --builddirectory has not been passed while the latter will generally not be null (except when build-system is none).

•   The dest-directory (--destdir) is undefined for all build steps except the install build step (will be output as null or absent). For the same reason, --destdir should only be passed for install build step.

    Note that if not specified, this value is currently null by default.

•   The parallel value is subject to DEB_BUILD_OPTIONS. Notably, if that does not include the parallel keyword, then parallel field in the output will always be 1.

•   Most fields in the output can be null. Particular if there is no build system is detected (or when --buildsystem=none). Additionally, many of the fields can be null even if there is a build system if the build system does not use/set/define that variable.

  detect-hook-targets (EXEC, AJSON)
Synopsis: dh_assistant detect-hook-targets

Detects possible override targets and hook targets that dh(1) might use (provided that the relevant command is in the sequence).

**UNSAFE**: This command relies on the output of make. Even it its dry-run mode, make may execute commands from debian/rules. Avoid using on packages from untrusted sources, where you have not reviewed the packaging for backdoors.

The detection is based on scanning the rules file for any target that might look like a hook target and can therefore list targets that are in fact not hook targets (or are but will never be triggered for other reasons).

The detection uses a similar logic for scanning the rules file and is therefore subject to makefile conditionals (i.e., the truth value of makefile conditionals can change whether a hook target is visible in the output of this command). In theory, you would have to setup up the environment to look like it would during a build for getting the most accurate output. Though, a lot of packages will not have conditional hook targets, so the "out of the box" behaviour will work well in most cases.

The output looks something like this:

    {
       "commands-not-in-path": [
          "dh_foo"
       ],
       "hook-targets": [
          {
             "command": "dh_strip_nondeterminism",
             "is-empty": true,
             "package-section-param": null,
             "filename": "debian/rules",
             "target-name": "override_dh_strip_nondeterminism"
          },
          {
             "command": "dh_foo",
             "is-empty": false,
             "package-section-param": "-a",
             "filename": "debian/rules",
             "target-name": "override_dh_foo-arch"
          }
       ]
    }

In more details:

commands-not-in-path
    This attribute lists all the commands related to hook targets, which dh_assistant could not find in PATH. These are usually caused by either the command not being installed on the system where dh_assistant is run or by the command not existing at all.

    If you are using this command to verify an hook target is present, please double check that the command is spelled correctly.

hook-targets
    List over hook targets found along with additional information about them.

    command
        Attribute that lists which command this hook target is related too.

    target-name
        The actual target name detected in the debian/rules file.

    is-empty
        A boolean that determines whether dh(1) will optimize the hook out at runtime (see "Completely empty targets" in dh(1)). Note that empty override targets will still cause dh(1) to skip the original command.

    package-section-param
        This attribute defines what package selection parameter should be passed to dh_* commands used in the hook target. It can either be -a, -i or (if no parameter should be used) "null".

    filename
        This attribute reports which file the target was found it. In most cases, this will always be "debian/rules" though in case of include files, the target could appear in an include file. Note this attribute is not super reliable as make(1) only reports it for targets with a "recipe" (targets with commands inside them). When make does not provide the filename, dh_assistant blindly assumes the filename is "debian/rules" (as overrides via includes is not a commonly used feature).

        Note this accuracy of this attribute is limited about what data dh_assistant can read out from the following command:

            LC_ALL=C make -Rrnpsf debian/rules debhelper-fail-me 2>/dev/null

This command accepts no options or arguments.

  detect-unknown-hook-targets (EXEC, AJSON, LINT)
Synopsis: dh_assistant detect-unknown-hook-targets [--output-format=json] [command-options]

Detects unknown and possibly misspelled override targets and hook targets in debian/rules that will most likely not be used by dh(1).

**UNSAFE**: This command relies on the output of make. Even it its dry-run mode, make may execute commands from debian/rules. Avoid using on packages from untrusted sources, where you have not reviewed the packaging for backdoors.

This command differs from detect-hook-targets subtly in the scope. The detect-hook-targets will list all targets that looks like hook targets whether they are applicable or not. This command show all hook targets, for which a command cannot be found in any sequence. Accordingly, this command is better for linting purposes whereas detect-hook-targets is better if you want to know which hook targets are present. All the limitations listed in detect-hook-targets about scanning the rules file apply equally to this command.

This command will attempt will attempt to load any sequence add-on listed via build-dependencies and therefore these must be installed. Additional modules can be passed via --with like with dh(1) as needed.

This command will also need one of the following perl modules to be available: Text::Levenshtein, Text::LevenshteinXS, Text::Levenshtein::XS. The first one can be installed via apt install libtext-levenshtein-perl.

The text output is intended for human consumption and should be self-explanatory. Since it is not stable, it will not be documented. The JSON output looks something like this:

    {
       "unknown-hook-targets": [
          {
             "target-name": "execute_before_dh_instlal",
             "filename": "debian/rules",
             "candidates": [
                "execute_before_dh_install"
             ]
          }
       ],
      "hook-targets-for-disabled-commands": [
          {
             "filename": "debian/rules",
             "target-name": "override_dh_builddeb",
             "removed-by": "zz-debputy"
          }
       ],

    }

In more details:

unknown-hook-targets
    List of all the unknown hook targets found along with additional information about them.

    target-name
        The actual target name detected in the file (usually debian/rules).

    filename
        This attribute reports which file the target was found it. In most cases, this will always be "debian/rules" though in case of include files, the target could appear in an include file. Note this attribute is not super reliable as make(1) only reports it for targets with a "recipe" (targets with commands inside them). When make does not provide the filename, dh_assistant blindly assumes the filename is "debian/rules" (as overrides via includes is not a commonly used feature).

        Note this accuracy of this attribute is limited about what data dh_assistant can read out from the following command:

            LC_ALL=C make -Rrnpsf debian/rules debhelper-fail-me 2>/dev/null

    candidates
        When not null and not empty, each element in this list are names for likely candidates for the "correct" name of this target.

hook-targets-for-disabled-commands
    List of known hook targets found related to disabled commands along with additional information about them.

    target-name
        The actual target name detected in the file (usually debian/rules).

    filename
        This attribute reports which file the target was found it. In most cases, this will always be "debian/rules" though in case of include files, the target could appear in an include file. Note this attribute is not super reliable as make(1) only reports it for targets with a "recipe" (targets with commands inside them). When make does not provide the filename, dh_assistant blindly assumes the filename is "debian/rules" (as overrides via includes is not a commonly used feature).

        Note this accuracy of this attribute is limited about what data dh_assistant can read out from the following command:

            LC_ALL=C make -Rrnpsf debian/rules debhelper-fail-me 2>/dev/null

    removed-by
        If present, this denotes the dh add-on that removed the command from the sequence (thereby disabling this command for that package).

        Note this field is not present in all cases. As an example, as obsolete commands (such as dh_gconf) are not part of any sequence by the time they are marked as obsolete.

        If you (as a consumer) need to know whether a command is obsolete or the particular reason why a command was disabled, please file a feature request to get that data. The absence of removed-by is not guaranteed to imply the command is obsolete.

issues
    If present, then it is a list of one or more reasons why this output is definitely incomplete. Each element in the list is an object with the following keys:

    issue
        A key defining the issue. Currently, it is always load-addon, which signals that dh_assistant could not load the add-on listed in the addon key.

        Parsers should assume new issue types may appear in the future.

    addon
        If present, it defines the name of a dh sequence add-on that is related to the failure.

This command accepts the following options:

--output-format=FORMAT
    Request a certain type of output format. Valid values are text or json.

    The text format is intended for human consumption and may change between versions without any regard for machine consumption. If you want to use this command for machine consumption, please use the JSON format.

--no-linter-exit-code, --linter-exit-code
    These options control whether the command should exit with the linter exit code (2) or not (0) when an unknown target is found. By default, it uses the linter exit code when an unknown target is found.

--with addon, --without addon
    These options behave the same as the dh(1) options with the same name.

  list-commands (RJSON)
Synopsis: dh_assistant list-commands [--output-format=json] [command-options]

Load all dh sequence add-ons and extract a full list of all commands that will be invoked across all sequences. The command makes no attempt to filter out commands that will not be run due to override targets or due to certain sequences not being run (by dh or at all).

As the command will attempt to load all plugins, they must be installed.

The text output is intended for human consumption and should be self-explanatory. Since it is not stable, it will not be documented. The JSON output looks something like this:

    {
       "commands": [
          {
             "command": "dh_auto_build"
          },
          {
             "command": "dh_auto_clean"
          },
          [... more commands listed here... ]
       ],
       "removed-commands": [
           {
             "command": "dh_gconf"
          },
       ]
       "issues": [
            {
                "issue": "load-addon",
                "addon": "foo"
            }
       ]
    }

commands
    The top level key containing the list of all commands. Each element in the list are an object and can have the following keys:

    command
        The name of the command.

        While most commands are resolved via PATH, a sequence add-on could register a command via a full path (by passing the path search). If so, the command provided in this output will also use the full path.

disabled-commands
    The top level key containing the list of all known commands that have been disabled. Each element in the list are an object and can have the following keys:

    command
        The name of the command.

        While most commands are resolved via PATH, a sequence add-on could register a command via a full path (by passing the path search). If so, the command provided in this output will also use the full path.

    removed-by
        If present, this denotes the dh add-on that removed the command from the sequence (thereby disabling this command for that package).

        Note this field is not present in all cases. As an example, as obsolete commands (such as dh_gconf) are not part of any sequence by the time they are marked as obsolete.

        If you (as a consumer) need to know whether a command is obsolete or the particular reason why a command was disabled, please file a feature request to get that data. The absence of removed-by is not guaranteed to imply the command is obsolete.

issues
    If present, then it is a list of one or more reasons why this output is definitely incomplete. Each element in the list is an object with the following keys:

    issue
        A key defining the issue. Currently, it is always load-addon, which signals that dh_assistant could not load the add-on listed in the addon key.

        Parsers should assume new issue types may appear in the future.

    addon
        If present, it defines the name of a dh sequence add-on that is related to the failure.

This command accepts the following options:

--output-format=FORMAT
    Request a certain type of output format. Valid values are text or json.

    The text format is intended for human consumption and may change between versions without any regard for machine consumption. If you want to use this command for machine consumption, please use the JSON format.

--with addon, --without addon
    These options behave the same as the dh(1) options with the same name.

  list-guessed-dh-config-files (AJSON)
Synopsis: dh_assistant list-guessed-dh-config-files [command-options]

Load all dh sequence add-ons declaratively depended on, determine the full list of commands could be relevant for this source package and for each command used, then attempt to guess which "config files" these commands are interested in.

The command will include config files for commands that are not active with current add-ons, since the commands might be run manually from hook targets.

Note this command only guesses "per command config files". Standard global config files such as debian/control, debian/rules, and debian/compat are not included in this output.

As the command name implies, the resulting output is not a full list (and will never be). The dh_assistant tool have to derive this from optional metadata that commands can choose to provide and dh_assistant has no means to validate that this metadata is up to date.

As the command will attempt to load all plugins referenced by the package, they must be installed.

The text output is intended for human consumption and should be self-explanatory. Since it is not stable, it will not be documented. The JSON output looks something like this:

    {
       "config-files": [
          {
             "commands": [
                {
                   "command": "dh_autoreconf_clean"
                   "is-active": true
                }
             ],
             "file-type": "pkgfile",
             "pkgfile": "autoreconf.before"
          },
          {
             "commands": [
                {
                   "command": "dh_installgsettings"
                   "is-active": true
                }
             ],
             "file-type": "pkgfile",
             "pkgfile": "gsettings-override"
          },
          # [ ... more entries here ...]
       ],
       "issues": [
           {
                "issue": "load-addon",
                "addon": "foo"
           }
       ]
    }

config-files
    The top level key containing the list of all config-files. Each element in the list are an object and can have the following keys:

    file-type
        The type of config file detected. At the time of writing, this will either be pkgfile or path. However, other values may appear in the future.

        When it is pkgfile, then the config file is a debhelper pkgfile (named after the pkgfile sub in Debian::Debhelper::Dh_Lib that locates the file). The value denoted by the pkgfile key will be the stem of the pkgfile (the install in debian/package. install).

    pkgfile
        When file-type is pkgfile, this key defines the name stem of the pkgfile. An example, this will be install for dh_install(1)'s config file and docs for dh_installdocs(1)'s config file.

        When file-type is not pkgfile, then this key will be absent.

        Typically names for these files are:

             debian/PKGFILE
             debian/PACKAGE.PKGFILE

        However, there are more variants caused by --name plus architecture specific suffixes.

    path
        When file-type is path, this key defines the static path of the configuration. An example, this will be debian/clean for dh_clean(1)'s config file and debian/not-installed for dh_missing(1).

        When file-type is not path, then this key will be absent.

    internal
        This key may exist and any value for it is not standardized. Use at own peril.

        It used for document certain specific implementation details such as bug compatibility and may change as the situation changes.

    commands
        This key will be a list with each element in it being an object with the following keys:

        command
            Name of the command that is interested in this config file. Multiple commands can be interested in the same config file. An example of this would be dh_installinit, dh_installsystemd and dh_installtmpfiles, which all reacts to (the now) deprecated tmpfile pkgfile. In the particular case, only one command reacts to the file for a given compat level (but that information is not available to dh_assistant and therefore is not available in this output either).

        is-active
            A boolean that determines whether the command is active with the loaded sequences. When false, the command is known to debhelper, but it is not run automatically via dh. The command might be explicitly removed by a sequence, marked as obsolete or possibly known to debhelper a command that would activate in a different command level (than the one currently active).

            Note that commands that are not "active" can often still be invoked manually from debian/rules via hook targets. Therefore, this reflects whether dh would call the command directly or provide its standard hook targets for the command.

        removed-by
            If present, this denotes the dh add-on that removed the command from the sequence (thereby disabling this command for that package).

            Note this field is not present in all cases regardless of the value of is-active. As an example, as obsolete commands (such as dh_gconf) are not part of any sequence by the time they are marked as obsolete.

            If you (as a consumer) need to know whether a command is obsolete or the particular reason why a command was disabled, please file a feature request to get that data. The absence of removed-by plus is-active being false is not guaranteed to imply the command is obsolete.

issues
    If present, then it is a list of one or more reasons why this output is definitely incomplete. Each element in the list is an object with the following keys:

    issue
        A key defining the issue. Currently, it is always load-addon, which signals that dh_assistant could not load the add-on listed in the addon key.

        Parsers should assume new issue types may appear in the future.

    addon
        If present, it defines the name of a dh sequence add-on that is related to the failure.

This command accepts the following options:

--with addon, --without addon
    These options behave the same as the dh(1) options with the same name.

  log-installed-files (BLD)
Synopsis: dh_assistant log-installed-files -ppkg [--on-behalf-of-cmd=dh_foo] path ...

Mark one or more paths as installed for a given package. This is useful for telling dh_missing(1) that the paths have been installed manually.

The --on-behalf-of-cmd option can be used by third-party tools to have dh_assistant list them as the installer of the provided paths. The convention is to use the basename of the tool itself as its name (e.g. dh_install).

Please keep in mind that:

•   No glob or substitution expansion is done by dh_assistant on the provided paths. If you want to use globs, have the shell perform the expansion first.

•   Paths must be given as relative to the source root directory (e.g., debian/tmp/...)

•   You can provide a directory. If you do, the directory and anything recursively below it will be considered as installed. Note that it is fine to provide the directory even if paths inside of it has been excluded as long as the directory is fully "covered".

•   Do not worry about providing the same filename twice in different invocations to dh_assistant due to -arch / -indep overrides. While it will be recorded multiple internally, dh_missing(1) will deduplicate when it parses the records.

Note this command only marks paths as installed. It does not actually install them - the caller should ensure that the paths are in fact handled (or installed).

  restore-file-on-clean (BLD)
Synopsis: dh_assistant restore-file-on-clean FILE ...

This command will take a backup of listed files and tell dh_clean(1) to restore them when it runs.

Note that generally you do not need to restore modified files on clean. Often you can get away with just removing them if they are regenerated anyway (which is the most common case for files being modified during builds). Use this command when something taints a file and the build does not cope with the file being removed.

The file is stored in debian/.debhelper. If you remove this directory manually without calling dh_clean(1) then your dh_assistant provided backup is gone permanently and the restore will never occur. At this point, only a version control system or another backup can restore the files.

The command has the following limitations:

No thread-safety - concurrency will corrupt the restore
    The command relies on updating an internal index and concurrent writes will cause it to be corrupt.

    While most dh_* commands does not use the underlying function, any of them could do so. Avoid running another dh_* command while dh_assistant processes this command (especially running multiple concurrent instances of dh_assistant restore-file-on-clean is asking for corruption!).

Files only, not directories nor symlinks to files
    This command will only restore files; not directories or symlinks to files. It will reject any non-files.

    Additionally, if the directory containing the file is removed, the restore will fail (as debhelper does not track the directory, it cannot restore it reliably). If this happens, you can do a mkdir to restore the directory and run dh_clean(1) again to get the files back. After that, consider what went wrong and whether you are using the correct tool(s).

Strict file names
    All filenames must be relative to the package root (without using the ./ prefix). No hidden files (that is any file starting with a period .) and no version control directories (such as CVS). The checks are best effort.

    These checks are here to ensure you do not accidentally trash important data that would help you undo mistakes.

Heavy duty
    The command takes a full copy of all files you pass it. This is fine for a handful of small files, which is the intended use-case. If you find yourself passing 10+ files or very large files, you might be applying a sledgehammer where you needed a different tool.

  compat-upgrade-checklist (EXEC)
Synopsis: dh_assistant compat-upgrade-checklist [--target-compat N]

This command generates a compat upgrade checklist for the current package.

The upgrade checklist is intended as an aid for contributors that upgrade a package to a newer compat level. Where possible, dh_assistant will attempt to detect whether some of the items are likely to be irrelevant and mark them as such. The logic will in many cases be a heuristic that can have false-positives and false-negatives.

The output is a markdown based checklist template aimed at being human-readable (output stability is not a goal). Typically, the user will want to direct standard output and then edit the checklist as they process to a file a la:

    dh_assistant compat-upgrade-checklist > debian/compat-upgrade-checklist.md
    editor debian/compat-upgrade-checklist.md
    # Iterate through the checklist, tweak the packaging, cross off items from the checklist (rinse and repeat)
    # Finally, remove the checklist.
    rm -f debian/compat-upgrade-checklist.md  # when the migration is complete

The command will provide a checklist up to latest stable compat level or the compat level provided via the --target-compat option.

This command accepts the following options:

--target-compat N
    Request the upgrade checklist to stop at the provided compat level rather than the highest stable compat level. This option can be used to limit the checklist to a given compat level or request checklists for experimental compat levels.

    The option cannot be used to generate a checklist for downgrading to a previous compat level. Trying to do so will result in an error message.

Note: If you run this command from a git checkout of debhelper, the behavior is slight different, since it will not correctly track which compat levels are stable (it is a build-time inserted property). As such, you will see experimental compat levels in the checklists by default, and they will not be marked as such. If you use the git checkout, it falls on you to be extra careful with these limitations of the generated checklist.

  supports (CFFA)
Synopsis: dh_assistant supports COMMAND

This command is a scripting aid to programmatically determine whether dh_assistant knows about a given subcommand. Pass the name of a subcommand and this command will exit successfully if the subcommand was known and unsuccessfully otherwise.

COMMAND TAGS
Most commands have one or more of the following "tags" associated with them. Their meaning is defined here.

EXEC
    This command will or may execute content from the package. Do not run on untrusted packages.

    Note: This tag only applies if the command will out of the box be unsafe. As an example, commands that parse the output of make is inherently unsafe, because it is trivial make to have make run code even in --dry-run mode. As a counter example, commands that only loads dh add-ons will be considered safe, because PERL5LIB is assumed to be curated to only include trusted plugins.

AJSON
    The command always provides JSON output. See "JSON OUTPUT" for details.

OJSON
    The command *can* provide JSON output via --output-format=json, but does not do so by default. See "JSON OUTPUT" for details when using --output-format=json.

LINT
    The command is or can be used for linting purposes. This command will exit with code 2 when an important issue is found. Be careful if the command is also tagged with EXEC. When this happens, the command should only be used on trusted content (see the EXEC tag for details).

    Note that commands may have options that redefine what is considered an "important" issue.

CRFA
    Mnemonic "Can be Run From Anywhere"

    Most commands must be run inside a source package root directory (a directory containing debian/control) because debhelper will need the package metadata to lookup the information. Any command with this tag are exempt from this requirement and is expected to work regardless of where they are run.

BLD The command is intended to be used as a part of a package build. It may leave artifacts behind that will need a dh_clean(1) invocation to remove.

JSON OUTPUT
Most commands uses JSON format as output. Consumers need to be aware that:

•   Additional keys may be added at any time. For backwards compatibility, the absence of a key should in general be interpreted as null unless another default is documented or would be "obvious" for that case.

•   Many keys can be null/undefined in special cases. As an example, some information may be unavailable when this command is run directly from the debhelper source (git repository).

The output will be prettified when stdout is detected as a terminal. If you need to pipe the output to a pager/file (etc.) and still want it prettified, please use an external JSON formatter. An example of this:

     dh_assistant supported-compat-levels | json_pp | less

SEE ALSO
debhelper(7)

This program is a part of debhelper.