Project: CFEngine (Provisioning / Automation & Configuration)
File: CONTRIBUTING.md

Thanks for considering contributing to CFEngine! We take pull-requests and we have a public . Discussion is taking place on and on the mailing list. You'll find us chatting on the Libera.chat IRC channel . Normally, bug fixes have a higher chance of getting accepted than new features, but we certainly welcome feature contributions. If you have an idea for a new feature, it might be a good idea to open up a feature ticket in our and send a message to dev-cfengine mailing list, before actually contributing the code, in order to get discussion going. Merged features and larger changes will be released in the first minor release (i.e. x.y.0). Please note that such pull requests should be ready for merging (i.e. adjusted for any feedback) at least two months before in order to make it to the first minor release. If you are not very familiar with Git or GitHub, you can look at our , later in this document. When submitting your pull request, please make sure you: Follow our . Address only one issue/feature. Smaller pull requests are generally better. Usually a Pull Request will have only one commit. Add tests. C functions should have unit tests. Promise types, attributes, and functions should have acceptance tests. Pay attention to review comments and CI results. We have code analysis and tests which run when you submit your PR. You may have to make some changes. Check that you don't have any merge conflicts. (Rebase on master or target branch). Tidy up the commit log by squashing commits and . Add one or more to the commit(s). Become familiar with the Northern.tech AS Contributor statement* as described in the file. Use the following format for the PR title: ``` CFE-1234: Title (3.12) ``` Omit the first part if there is no related ticket. Omit the last part if the PR is for master branch. If the PR has only 1 commit, the title and description should match the title and body of the commit message. If the PR has multiple commits, summarize. See: . CFEngine is built from several different repositories. Sometimes a change is needed in multiple repositories. When possible, try to make changes compatible with the master version of the other repositories. While our Jenkins Pipeline can handle multiple Pull Requests, Travis does not. If you are making a breaking change in one repository which has to be merged together with another pull request, make this very clear. Put this in the pull request description (first comment); ``` Merge together: cfengine/core#1234 cfengine/buildscripts#333 ``` If the change is needed for a bigger feature, make that feature a separate pull request. The bigger PR will likely take some time to get reviewed, and discussed, while smaller changes can be merged quickly. Each commit should be a valid change and make sense on its own. It is often a good idea to make commits as small as possible. Normally, each commit should include only 1 bug fix, only 1 refactoring, or only 1 new feature. Tests which test a new feature can be in the same commit as the feature. If you add tests for other issues or features, they should be in a separate commit. Writing good commit messages, and having a clear history of git commits is

It helps those reviewing your code, when merging and in the future. Good commit messages also increase the quality of the generated changelogs for each release. It is important that the commit message is sufficiently explicit/descriptive. As an example: ``` Fixed execresult function ``` This is not good, because it doesn't really say what was wrong. Here are some better examples: ``` Policy function execresult() no longer crashes when passed empty string ``` ``` Fixed memory leak in policy function execresult() ``` Here is an example of our commit messages: ``` Fixed memory leak in: differences(), intersection(), unique() They all use `FnCallSetOp()` internally, which was lacking free for some error handling return paths. Changelog: Title Ticket: ENT-4586 ``` A commit message consists of 3 parts; a title, a body, and metadata. The 3 parts are separated by empty lines. The body and metadata parts are optional. The first line of the commit message is called the title. It should not have punctuation (like `.`/`!`) on the end of the line. It should not exceed 80 characters. In a short sentence it explains the change in the commit. If the commit includes a change in code, as well as a test, it doesn't need to mention the test. Past tense is preferred, especially when the title is used in the changelog. The body can be several sentences. They should have proper punctuation, ending sentences in `.`/`!`. Wrap lines before 80 characters, so the width of `git log` is consistent. It should explain the change in detail, and can give examples, implementation details, etc. Using some markdown syntax is okay, but not required. Commit messages and changelog entries are considered plain text. Sometimes markdown can make them more clear, and the automatic pull request description on GitHub looks nicer. The metadata part is one or more lines of `Keyword: Value`. We mainly use 3 keywords: ``` Changelog: Title Ticket: CFE-1234 Signed-off-by: Ole Herman Schumacher Elgesem <ole@northern.tech> ``` (`Signed-off-by` is added by `git commit -s`). One exception is the line automatically added by `git cherry-pick -x`, which looks like this: ``` (cherry picked from commit fca949fdb4b9691338e316b3675d8e5a4e9082b9) ``` If your change only affects one feature, component or part of the git repo, you can prefix the title: ``` CONTRIBUTING.md: Improved instructions for commit messages ``` This is helpful because it clearly communicates that the change only affects this markdown file. The same can be said for only affecting one component(binary): ``` cf-net: Fixed networking issues on windows ``` Most new features and fixes should have an entry in the `ChangeLog` file. We have an automatic way of generating them before the release, by properly formatting commit messages. To write arbitrary message in the ChangeLog: `Changelog: <message>` To use the commit title line in the ChangeLog: `Changelog: Title` To use the entire commit message in the ChangeLog: `Changelog: Commit` To not generate an entry in the ChangeLog: `Changelog: None` `Changelog` entry is in past tense, and explains the impact to users. Changelog entries should be written in a way that is understandable by our users. This means that references to implementation details are not appropriate, leave this for the non-changelog part of the commit message. It is the behavior change which is important. Changes which don't affect users, like changes in tests or in tools which are not packaged, should not have a changelog

All changelog entries should also include a reference to a ticket: `Ticket: CFE-1234` Note that the `Changelog` and `Ticket` entries must be in a commit message and not the description of a PR. Sometimes is necessary to redact a `Changelog` entry, for example a commit needs to be reverted, or it's already been mentioned in another `Changelog` entry in another repository. When this is necessary, use the `Cancel-Changelog` keyword with the commit of the entry you wish to redact: `Cancel-changelog: 19cd387` Most changes should have a ticket number, referring to a ticket on our bug tracker: https://northerntech.atlassian.net/ Add it to the commit message as in the example above. Our coding style is loosely based on Allman-4 and the . Keep in mind that these are guidelines, there will always be some situations where exceptions are appropriate. Feel free to use `clang-format` to format new code you submit. (Our configuration is in `.clang-format`). 4 spaces per indentation, no tabs. Fold new code at 78 columns. Do not break string literals. Prefer having strings on a single line, in order to improve search-ability(grep). If they do not fit on a single line, try breaking on punctuation. You can surpass the 78 column limit if necessary. Use single spaces around operators, but not before semicolon: ```c int a = 2 + 3; int b = 2 * (a - 2); if (a > b) ``` Place pointer star to the right, next to the name it belongs to: ```c int *a; char b, c; const char *const d; ``` Curly brackets on separate lines. Except in a do-while loop, to avoid confusion with a while loop: ```c do { // ... } while (condition); ``` Except at the end of a struct type definition: ```c typedef struct _Name { // ... } Name; ``` Type casts should be separated with one space from the value: ```c bool ok = true; int res = (int) ok; char msg = (char ) malloc(64 sizeof(char )); ``` Automake is based on make. In make and automake files, tabs have a special meaning. Some places you have to use tabs, other places you cannot use tabs. Always use tabs for make targets (required by make): ``` run-coverage: <TAB>-$(MAKE) check -k ``` For consistency, always use tabs to indent multi line lists (optional in make): ``` AM_CFLAGS = \ <TAB>$(OPENSSL_CFLAGS) \ <TAB>$(PCRE2_CFLAGS) \ <TAB>$(ENTERPRISE_CFLAGS) ``` Inside an `if`, you cannot indent with tabs (lines will be silently skipped): ``` if !BUILTIN_EXTENSIONS bin_PROGRAMS = cf-key cfkeyLDADD = libcf-key.la cfkeySOURCES = endif ``` We prefer to not indent at all in these cases, if you have to, use 4 spaces. Keep in mind that code should be readable by non C experts. If you are a Guru, try to restrain yourself, only do magic when absolutely necessary. Avoid code duplication. Make a variable or a function instead of copy-pasting the same patterns. Helper functions which are only used in the same file should be declared `static`. If you want to test the `static` functions, you can `#include` the `.c` file in the unit test. Avoid abbreviations. Welcome to "modern" C (C99). Declare variables where they are needed, not at the beginning of a function / block. Declare index inside for loop: ```c for (int i = 0; i < n; ++i) ``` Conditionals: Don't include assignments inside

Put them on the line before. Unless they avoid great repetition*. Always* use curly braces: ```c if (ready) { printf("Ready!\n"); } ``` A conditional with an empty body should have curly braces, and a comment: ```c while (ready) { // Log message already printed above } ``` Switch-case deliberate fall through: It should be explicitly indicated with a specific comment: `// fall through` or `/ fall through /` ```c switch(x) { case 1: case 2: // ... // fall through // Optional comment explaining why case 3: // ... break; default: // ... break; } ``` Variable names: Describe what the variable is. Are English words with underscores: `string_index` Boolean variable names should make an `if`/`while` sensible: `if (moredata)` / `while (moredata)` Function names: Are `CamelCase` (with first letter capital). Describe what the function does. Namespaces: Don't exist in C. But we can pretend, using underscores in function names: `StrList_BinarySearch()` Structs: Names are `CamelCase` (with first letter capital). Use the common typedef pattern: ```c typedef struct _Point { float x; float y; } Point; ``` Don't add a trailing `_t` or similar for typedefs. Structs and functions which modify them are similar to classes and methods in other languages. Method names should start with the struct name. The first parameter should be the "self" pointer: ```c void SeqAppend(Seq seq, void item); ``` Document using Doxygen (within reason), preferably in the `.c` files, not the header files. Minimize use of global variables. Use pure functions when possible: Functions with no / few side effects are easier to reuse. Use `const` parameters to show that they are not altered. Functions which expect their arguments to be non-NULL should assert this at the top: ```c size_t SeqLength(const Seq *seq) { assert(seq != NULL); return seq->length; } ``` Not necessary all the time, avoid duplication. A wrapper like this doesn't need the asserts: ```c bool SaveXmlDocAsFile(xmlDocPtr doc, const char file, const Attributes a, NewLineMode newlinemode) { return SaveAsFile(&SaveXmlCallback, doc, file, a, newlinemode); } ``` It's more appropriate to put the asserts close to the code which dereferences the pointers. Variable initialization: Don't initialize variables unless they need an initial value. Unnecessary initialization silences important compiler warnings. Put the declaration and initialization in the same statement (line). ```C time_t now = time(NULL); ``` Constants: Constify what can be `const`. A pointer to an immutable string: ```c const char *string; ``` An immutable pointer to a mutable string: ```c char *const string; ``` An immutable pointer to an immutable string: ```c const char *const string; ``` The `const` keyword applies to the left, unless it is the first, then it applies to the right. Types: Assign and compare using the correct "type" literal: ```c float temperature = 0.0; int dollars = 10; char string_terminator = '\0'; char *name = NULL; if (name == NULL && dollars <= 0 && temperature <= -10.0) { // :( } ``` Conditions: Use explicit comparisons: ```c if (data != NULL) ``` Have the literal (constant) to the right side, so it reads well: ```c if (age >= 33) ``` NEVER* compare to `true`: `if (data == true)` (`true` is `1`) Error handling: Functions which can fail should return error code (int) or success/failure (bool). Compiler can enforce checking of return value, output of function can be in an output parameter

Functions which have valid positive return values can use negative numbers for errors. `true`(`bool`) and `0`(`int`) should signify success. Only return an error code (`int`) when there are multiple different return values for different errors. If a function can only return `0` (success) or `-1` (error) use `bool` instead. `Destroy` functions should accept NULL pointers (similar to `free()`). Don't use `static` variables that change, since they are not thread-safe. Sizes of stack-allocated buffers should be deduced using `sizeof()`. Never hard-code the size (like `CF_BUFSIZE`). Avoid using type casts, unless absolutely necessary. Usually a compiler warning is better satisfied with correct code rather than using a type cast. | Type | Format string | | :-- | :- | | `char *` | `%s` | | `int` | `%d` | | `unsigned int` | `%du` | | `long` | `%l` | | `unsigned long` | `%lu` | | `size_t` | `%zu` | | `ssize_t` | `%zd` | | `intmax_t` | `%jd` | | `uintmax_t` | `%ju` | See `man 3 printf` for a more complete table. For other integer types without a format, cast `signed` types to `intmaxt` and `unsigned` types to `uintmaxt`. CFEngine outputs messages about what it's doing using the `Log()` function. It takes a `LogLevel` enum, mapping closely to syslog priorities. Please try to do the following when writing output messages. `LOGLEVELCRIT`: For critical errors, where process cannot / should not continue running, exit immediately. `LOGLEVELERR`: Promise failed or other errors that are definitely considered bad / not normal. `LOGLEVELWARNING`: Something unusual happened that the user should investigate. Should be severe enough to warrant investigating further, but not as severe as a definitive error/bug. `LOGLEVELNOTICE`: Important information (not errors) that must not be missed by the user. For example cf-agent uses it in files promises when change tracking is enabled and the file changes. `LOGLEVELINFO`: Useful high level information about what the process is doing. Examples: Changes performed to the system, for example when a promise has been repaired. Server denies access to client based on `access_rules`. `LOG_LEVEL_VERBOSE`: Log human readable* progress info useful to users (i.e. sysadmins). Also errors that are unimportant or expected in certain cases. `LOGLEVELDEBUG`: Log anything else (for example various progress info). Try to avoid "Entering function Foo()", but rather use for "While copying, got reply '%s' from server". Please keep in mind that some components like `cf-serverd` handle very large sets of data / connections and logs can become spammy. In some cases it might be appropriate to create error / warning summaries instead of outputting a log message every time an event occurs. Do not decorate with symbols or indentation in messages and do not terminate the message with punctuation. Let `Log()` enforce the common formatting rules. When quoting strings, use single quotes, e.g. "Some stuff '%s' happened in '%s'. Keep in mind context, e.g. write "While copying, insufficient permissions" rather than "Insufficient permissions". Use output sparingly, and use levels appropriately. Verbose logging tends to get very verbose. Use platform-independent `GetErrorStr()` for `strerror(errno)`. Write for example `Log(LOGLEVELERR, "Failed to open ... (fopen: %s)", GetErrorStr());` Normally, try to keep each message to one line of output, produced by one call to `Log()`. Normally, do not circumvent `Log()` by writing to stdout or stderr. The CFEngine codebase can be usefully thought of as a few separate components: utilities (libutils), parsing (libpromises), evaluation (libpromises), actuation (mostly in cf-agent), network

Since around 2016, the structure of the codebase has undergone some change. The goal of the restructuring is to isolate separate components with explicit dependencies, and provide better unit test coverage. For a general introduction to the tools, please read the man pages/documentation. These are replacement functions in cases where autoconf cannot find a function it expected to find on the platform. CFEngine takes an approach of relying on the platform (typically POSIX) as much as possible, rather than creating its own system abstraction layer. Contains generally useful data structures or utilities. The key point about libutils is that it is free of dependencies (except libcompat), so it does not know about any CFEngine structures or global state found in libpromises. Some examples of often used files (not meant to be an exhaustive list): sequence.h: Collection of ordered elements (Loosely based on glib GSequence). map.h: General purpose map (hash table). set.h: General purpose set, a wrapper of Map. writer.h: Stream writer abstraction over strings and FILEs. string_lib.h: General purpose string utilities. logging.h: Log functions, use Log() instead of printf. ip_address.h: IP address parsing. file_lib.h: General purpose file utilities. misc_lib.h: Really general utilities. Contains the networking layer for CFEngine. All of this was in libpromises previously. Ideally it would be completely separate, without depending on libpromises, but we're not there yet. See JIRA Epic for details on status. This is the remainder of the old src directory, that which has not been categorized. The roadmap for the project remains to leave libpromises as a component for evaluation. cf3.defs.h: Contains structure definitions used widely. generic_agent.h: Common code for all agent binaries. parser.h: Parse a policy file. syntax.h: Syntax utilities and type checking. mod_???.c: Syntax definitions for all promise types (actuation modules). eval_context.h: Header for EvalContext, keeper of evaluation state. expand.c: Evaluates promises. policy.h: Policy document object model, essentially the AST output of the parsing stage. evalfunction.c: Where all the built-in functions are implemented. locks.h: Manages various persistent locks, kept in a local database. sysinfo.c: Detects hard classes from the environment (OS, IP, etc.) Things which should be moved out of libpromises: crypto.h: Crypto utilities for some reason still tied to evaluation state. files_???: File utilities we haven't been able to decouple from evaluation. Things you should not use in libpromises cf3.extern.h: Remaining global variables. prototypes3.h: The original singular header file. item_lib.h: Item is a special purpose list that has been abused for unintended purposes. assoc.h: An lval-rval pair, deprecated in favor of EvalContext symbol table. scope.h: Old symbol table, this will move into EvalContext. See the documentation for an introduction to cf-agent and the other components. Since cf-agent is (arguably) the most important component here is a more technical description of how it works, both during first time setup (bootstrap) and regular operation. Note that most of the binaries evaluate policy so there are many similarities to cf-agent. The following outlines the normal execution of a cf-agent run. Read options and gather these in GenericAgentConfig. Create an EvalContext and call GenericAgentConfigApply(ctx, config). Discover environment and set hard classes, apply to EvalContext. Parse input policy file, get a Policy object. Run static checks on Policy object. Evaluate each Bundle in bundlesequence. Write reports to disk. The following outlines the steps taken by agent during a successful bootstrap to a policy server. Remove all files in `inputs` directory Write built-in

Write policy server address or hostname, as was the argument to `--bootstrap` option, to `policy_server.dat`. If the host was bootstrapped to the machine's own IP address, then it is a policy server, and the file `state/ampolicyhub` is touched as marker. cf-agent runs using `failsafe.cf` as input file: Runs `cf-key` to generate `localhost.{priv,pub}` keys inside `ppkeys` directory. Fetches policy files from the policy server. Starts `cf-execd` Runs `cf-agent -f update.cf` Agent finishes. `cf-execd` continues to run `cf-agent` periodically with policy from `inputs` directory. It is extremely important to have automated tests for all code, and normally all new code should be covered by tests, though sometimes it can be hard to mock up the environment. There are two types of tests in CFEngine. Unit tests are generally preferable to acceptance tests because they are more targeted and take less time to run. Most tests can be run using `make check`. See below. Unit tests*. Unit tests are a great way of testing some new module (header file). Ideally, the new functionality is written so that the environment can be easily injected and results readily verified. Acceptance tests. These are tests that run cf-agent* on a policy file that contains test and check bundles, i.e. it uses CFEngine to both make a change and check it. See also script tests/acceptance/testall. Tip: In order to trigger assert() calls in the code, build with `--enable-debug` (passed to either `./autogen.sh` or `./configure`). If you get very large binary sizes you can also pass `CFLAGS='-g -O0'` to reduce that. We strive to always increase code coverage. If you wish to generate code coverage information then you must autogen or configure with --enable-debug and --enable-coverage as well as ensure lcov is installed (typically an lcov package is available in a distribution). We use gcov to instrument and process coverage information. .gcno files are generated at compile-time and will not be regenerated if the source code does not change. So be careful about cleaning those files. .gcda files are like index files which can be used to generate the .gcov files which lcov uses to generate lcov.info and the HTML report in the coverage-html directory. Many IDEs and editors expect a <root>/coverage/lcov.info summary of coverage information. After running `make check` you can run `make coverage` and generate this lcov.info summary for use with other tools. If you wish to only run a few tests which will add to coverage data you can update lcov.info with `make collect-coverage` which will only collect coverage data, not compile or run any tests. For the atom editor, install the package atom-lcov-info. Note that some acceptance tests are considered to be unsafe because they modify the system they are running on. One example is the tests for the "users" promise type, which does real manipulation of the user database on the system. Due to their potential to do damage to the host system, these tests are not run unless explicitly asked for. Normally, this is something you would want to do in a VM, so you can restore the OS to a pristine state afterwards. To run all tests, including the unsafe ones, you either need to be logged in as root or have "sudo" configured to not ask for a

Then run the following: ``` $ UNSAFE_TESTS=1 GAINROOT=sudo make check ``` Again: DO NOT do this on your main computer! Always use a test machine, preferable in a VM. It's important to have portability in a consistent way. In general we use autoconf to test for features (like system headers, defines, specific functions). So try to use the autoconf macros `HAVEDECLX`, `HAVESTRUCTY`, `HAVE_MYFUNCTION` etc. See the . It is preferable to write feature-specific ifdefs, instead of OS-specific, but it's not always easy. If necessary use these platform-specific macros in C code: Any Windows system: Use `_WIN32`. Don't use `NT`. mingw-based Win32 build: Use `MINGW32`. Don't use `MINGW`. Cygwin-based Win32 build: Use `CYGWIN`. Don't use `CFCYG`. OS X: Use `APPLE`. Don't use `DARWIN`. FreeBSD: Use `FreeBSD`. Don't use `FREEBSD`. NetBSD: Use `NetBSD`. Don't use `NETBSD`. OpenBSD: Use `OpenBSD`. Don't use `OPENBSD`. AIX: Use `_AIX`. Don't use `AIX`. Solaris: Use `sun`. Don't use `SOLARIS`. Linux: Use `linux`. Don't use `LINUX`. HP/UX: Use `hpux` (two underscores!). Don't use `hpux`. Finally, it's best to avoid polluting the code logic with many ifdefs. Try restricting ifdefs in the header files, or in the beginning of the C files. For very small / simple changes, you can open a PR by clicking the edit buttons in the GitHub UI. For most changes, it is preferable to work locally, using git. This is a suggested outline for those unfamiliar with working with GitHub. It does, however, assume a familiarity with the basics of using git so it does not attempt to provide every detail of that. You will be working with three git repositories: the central one on Github, your fork on Github and your local clone. Within Github, make your fork of the central CFEngine repository using the fork icon on the . Your fork lives at `https://github.com/your-username/core` (by default). Clone your fork, there is a "Clone or Download" button, which shows the necessary information. For example: ``` $ git clone --recursive https://github.com/your-username/core $ cd core ``` (If you have set up your GitHub profile with your SSH key, you can use the SSH URLs instead, which might be more convenient). Replace `your-username` with your GitHub username, here and later. `--recursive` is needed to clone submodules, without it, you would have to run these commands separately: ``` $ git submodule init $ git submodule update ``` Now, add a `remote` reference to the `upstream` repository: ``` $ git remote add upstream https://github.com/cfengine/core ``` The result should look like this: ``` $ git remote -v origin https://github.com/olehermanse/core (fetch) origin https://github.com/olehermanse/core (push) upstream https://github.com/cfengine/core (fetch) upstream https://github.com/cfengine/core (push) ``` `origin` is your fork. This is the default for pushing and pulling. `upstream` is the central repository, managed by the CFEngine GitHub organization. You (probably) don't have access to push to `upstream`. Using these names are just a convention, you could change them, but we don't recommend it. Never work in the `master` branch; always use a separate branch for your topic. Prepare your topic on this topic-focussed branch. When it is ready, push it to your Github fork. ``` $ git checkout master $ git checkout -b mytopic ``` You can now make your changes. Build and test them when done: ``` $ ./autogen.sh --enable-debug && make -j4 && (cd tests/unit/ && make check) ``` Running all the tests is quite slow, because of many acceptance tests. Locally, it is usually sufficient to run unit tests, and select acceptance

Then, commit and push normally: ``` $ git add -p $ git commit $ git push ``` The default behavior of `git push` may or may not work for you, you can also specify where to push manually: ``` $ git push --set-upstream origin mytopic ``` On your fork at Github you should now see an additional branch `mytopic`. This is what you use for the pull request there. Pushing more commits or force pushing changed commits to the same branch will automatically update an open Pull Request which uses that branch. After you branched from `upstream/master` it is possible that someone else (or even you) commit conflicting changes to the `master` branch. To resolve these conflicts in your PR branch, use: ``` $ git fetch --all $ git rebase upstream/master ``` This will stop at the conflicting commit, and give you instructions to proceed. You will have to resolve conflicts and then run: ``` $ git rebase --continue ``` This might happen multiple times (1 for each commit). Once done, you will have to force push your changes to the PR branch: ``` $ git push -f ``` We want the commit history to be as easy to read and understand as possible. Sometimes we make more commits than necessary, and we want to squash them (combine them). A good tool for this is interactive rebase. On your PR branch, run: ``` $ git rebase -i upstream/master ``` This will open an editor (usually `vi` or `emacs`), with a list of your commits: ``` pick ac07e6d27 Added new policy function isrealdir() pick 001bd420b Fixed mistake in isrealdir() ``` `upstream/master` will be used as a starting point, and the commits / commands will be applied tofrom top to bottom of this list. To combine the 2 commits, replace `pick` with `squash` on the second line: ``` pick ac07e6d27 Added new policy function isrealdir() squash 001bd420b Fixed mistake in isrealdir() ``` This will squash the second commit into the first one (the one above). Save and close. Another editor will open, allowing you to update the commit message(s). Update it to reflect the current state of this commit, then save and close. Once you get comfortable with interactive rebase you can make more advanced changes, like squashing multiple commits, reordering commits, or dropping some commits. You may create conflicts, that you have to resolve, as described above. See also: Switch to local master branch: ``` $ git checkout master ``` Download changes from all remotes: ``` $ git fetch --all ``` Apply changes from the `upstream` `master` branch to our local `master` branch: ``` $ git rebase upstream/master ``` (You can also use `git pull`, but I find `rebase` a little easier when there are conflicts. `git pull` is a combination of `git fetch` and `git merge`.) Inspect the results: ``` $ git log ``` (Press `q` to quit `git log`). The latest (top) commit, should include `master` and `upstream/master` in parenthesis. This indicates that your local branch is up to date with `upstream`. If there are additional commits after the `upstream/master` commit, it means you committed some things on master, perhaps by

You can remove them, by doing: ``` $ git branch master-with-extra-commits $ git reset --hard upstream/master ``` You can, optionally, push your updated `master` branch to your GitHub fork: ``` $ git push ``` If you've already pushed some of the extra commits (on accident), you may have to add `--force`: ``` $ git push --force ``` However, normally this should not be necessary (!). `git` has some commands for working with submodules, for example: ``` $ git submodule update ``` This will update the submodule, checking out the correct commit for your current for your current branch. Please note that a submodule is like a normal git repo, with the `SHA` committed to the parent repo. In many situations, the easiest approach is to `cd` into the submodule and run normal `git` commands in there. You can add remotes, push, pull, rebase, fetch, etc. inside the submodule. If you want to make changes to a submodule (for example `libntech`). Follow the same general steps inside that folder. (Fork that repo on GitHub, set up your fork as a remote etc.) If you need to make changes to the `libntech` submodule, you will need to submit a PR to that repo: https://github.com/NorthernTechHQ/libntech The `libntech` PR has to be merged, before we can test your changes in `core`. This section is not for new contributors, but rather contains more specific guides which are useful to link to in some circumstances. Determine the commit to backport, use the first 6 or so characters of the sha1 (to make it unique). E.g. 80f198 for 80f198baeddcd5d1b9556d9a4890b648fe3c12c5 ``` First checkout the branch you are backporting to: $ git checkout --track upstream/<branch such as 3.10.x> ``` Next create a branch in which to work and for a PR: ``` $ git checkout -b backport-some-commit ``` If you are cherry picking your own commit simply use -x option ``` $ git cherry-pick -x 80f198 ``` `-x` adds: `"(cherry picked from commit 80f198baeddcd5d1b9556d9a4890b648fe3c12c5)"`` If you are cherry picking someone elses commit, use the -s option to make your involvement more obvious. ``` $ git cherry-pick -x -s 80f198 ``` `-s --signoff` adds: `"Signed-off-by: Committer Name <committer.email@northern.tech>"` Submit your change as a PR: ``` $ git push --set-upstream origin backport-some-commit ``` In the GitHub web UI you will need to create the PR and select the correct branch to submit to. If the cherry pick applied cleanly and you have merge rights, you may merge the change. If significant or risky changes were introduced in order to backport, ask for code review before merging. (Open a Pull Request to add instructions for other platforms). There is an Elisp snippet in `contrib/cfengine-code-style.el` which defines the project's coding style. Please use it when working with source code. The easiest way to do so is to add: ``` (add-to-list 'load-path "<core checkout directory>/contrib") (require 'cfengine-code-style) ``` and run: ``` ln -s contrib/dir-locals.el .dir-locals.el ``` On Windows the `atexit` function works but the functions registered there are executed after or concurrently with DLL unloading. If registered functions rely on DLLs such as pthreads to do locking/unlocking deadlock scenarios can occur when exit is called. In order to make behavior more explicit and predictable we migrated to always using a homegrown atexit system. RegisterCleanupFunction instead of atexit and DoCleanupAndExit instead of exit. If `Exit` or `exit` need to be called that is fine as they don't call atexit or cleanup functions. In some cases such as when exiting a forked process or in executables which don't register cleanup functions, exit() may be used but a comment should be added noting that this issue was