diff options
Diffstat (limited to 'Documentation/technical')
| -rw-r--r-- | Documentation/technical/api-config.txt | 2 | ||||
| -rw-r--r-- | Documentation/technical/api-oid-array.txt | 5 | ||||
| -rw-r--r-- | Documentation/technical/api-parse-options.txt | 4 | ||||
| -rw-r--r-- | Documentation/technical/api-trace2.txt | 1378 | ||||
| -rw-r--r-- | Documentation/technical/commit-graph-format.txt | 4 | ||||
| -rw-r--r-- | Documentation/technical/commit-graph.txt | 17 | ||||
| -rw-r--r-- | Documentation/technical/directory-rename-detection.txt | 4 | ||||
| -rw-r--r-- | Documentation/technical/pack-protocol.txt | 28 | ||||
| -rw-r--r-- | Documentation/technical/partial-clone.txt | 2 | ||||
| -rw-r--r-- | Documentation/technical/protocol-capabilities.txt | 18 | ||||
| -rw-r--r-- | Documentation/technical/protocol-v2.txt | 70 |
11 files changed, 1468 insertions, 64 deletions
diff --git a/Documentation/technical/api-config.txt b/Documentation/technical/api-config.txt index fa39ac9d71..7d20716c32 100644 --- a/Documentation/technical/api-config.txt +++ b/Documentation/technical/api-config.txt @@ -229,7 +229,7 @@ A `config_set` can be used to construct an in-memory cache for config-like files that the caller specifies (i.e., files like `.gitmodules`, `~/.gitconfig` etc.). For example, ---------------------------------------- +---------------------------------------- struct config_set gm_config; git_configset_init(&gm_config); int b; diff --git a/Documentation/technical/api-oid-array.txt b/Documentation/technical/api-oid-array.txt index 9febfb1d52..c97428c2c3 100644 --- a/Documentation/technical/api-oid-array.txt +++ b/Documentation/technical/api-oid-array.txt @@ -48,6 +48,11 @@ Functions is not sorted, this function has the side effect of sorting it. +`oid_array_filter`:: + Apply the callback function `want` to each entry in the array, + retaining only the entries for which the function returns true. + Preserve the order of the entries that are retained. + Examples -------- diff --git a/Documentation/technical/api-parse-options.txt b/Documentation/technical/api-parse-options.txt index 2b036d7838..2e2e7c10c6 100644 --- a/Documentation/technical/api-parse-options.txt +++ b/Documentation/technical/api-parse-options.txt @@ -198,8 +198,10 @@ There are some macros to easily define options: The filename will be prefixed by passing the filename along with the prefix argument of `parse_options()` to `prefix_filename()`. -`OPT_ARGUMENT(long, description)`:: +`OPT_ARGUMENT(long, &int_var, description)`:: Introduce a long-option argument that will be kept in `argv[]`. + If this option was seen, `int_var` will be set to one (except + if a `NULL` pointer was passed). `OPT_NUMBER_CALLBACK(&var, description, func_ptr)`:: Recognize numerical options like -123 and feed the integer as diff --git a/Documentation/technical/api-trace2.txt b/Documentation/technical/api-trace2.txt new file mode 100644 index 0000000000..fd1e628944 --- /dev/null +++ b/Documentation/technical/api-trace2.txt @@ -0,0 +1,1378 @@ += Trace2 API + +The Trace2 API can be used to print debug, performance, and telemetry +information to stderr or a file. The Trace2 feature is inactive unless +explicitly enabled by enabling one or more Trace2 Targets. + +The Trace2 API is intended to replace the existing (Trace1) +printf-style tracing provided by the existing `GIT_TRACE` and +`GIT_TRACE_PERFORMANCE` facilities. During initial implementation, +Trace2 and Trace1 may operate in parallel. + +The Trace2 API defines a set of high-level messages with known fields, +such as (`start`: `argv`) and (`exit`: {`exit-code`, `elapsed-time`}). + +Trace2 instrumentation throughout the Git code base sends Trace2 +messages to the enabled Trace2 Targets. Targets transform these +messages content into purpose-specific formats and write events to +their data streams. In this manner, the Trace2 API can drive +many different types of analysis. + +Targets are defined using a VTable allowing easy extension to other +formats in the future. This might be used to define a binary format, +for example. + +Trace2 is controlled using `trace2.*` config values in the system and +global config files and `GIT_TRACE2*` environment variables. Trace2 does +not read from repo local or worktree config files or respect `-c` +command line config settings. + +== Trace2 Targets + +Trace2 defines the following set of Trace2 Targets. +Format details are given in a later section. + +=== The Normal Format Target + +The normal format target is a tradition printf format and similar +to GIT_TRACE format. This format is enabled with the `GIT_TR` +environment variable or the `trace2.normalTarget` system or global +config setting. + +For example + +------------ +$ export GIT_TRACE2=~/log.normal +$ git version +git version 2.20.1.155.g426c96fcdb +------------ + +or + +------------ +$ git config --global trace2.normalTarget ~/log.normal +$ git version +git version 2.20.1.155.g426c96fcdb +------------ + +yields + +------------ +$ cat ~/log.normal +12:28:42.620009 common-main.c:38 version 2.20.1.155.g426c96fcdb +12:28:42.620989 common-main.c:39 start git version +12:28:42.621101 git.c:432 cmd_name version (version) +12:28:42.621215 git.c:662 exit elapsed:0.001227 code:0 +12:28:42.621250 trace2/tr2_tgt_normal.c:124 atexit elapsed:0.001265 code:0 +------------ + +=== The Performance Format Target + +The performance format target (PERF) is a column-based format to +replace GIT_TRACE_PERFORMANCE and is suitable for development and +testing, possibly to complement tools like gprof. This format is +enabled with the `GIT_TRACE2_PERF` environment variable or the +`trace2.perfTarget` system or global config setting. + +For example + +------------ +$ export GIT_TRACE2_PERF=~/log.perf +$ git version +git version 2.20.1.155.g426c96fcdb +------------ + +or + +------------ +$ git config --global trace2.perfTarget ~/log.perf +$ git version +git version 2.20.1.155.g426c96fcdb +------------ + +yields + +------------ +$ cat ~/log.perf +12:28:42.620675 common-main.c:38 | d0 | main | version | | | | | 2.20.1.155.g426c96fcdb +12:28:42.621001 common-main.c:39 | d0 | main | start | | 0.001173 | | | git version +12:28:42.621111 git.c:432 | d0 | main | cmd_name | | | | | version (version) +12:28:42.621225 git.c:662 | d0 | main | exit | | 0.001227 | | | code:0 +12:28:42.621259 trace2/tr2_tgt_perf.c:211 | d0 | main | atexit | | 0.001265 | | | code:0 +------------ + +=== The Event Format Target + +The event format target is a JSON-based format of event data suitable +for telemetry analysis. This format is enabled with the `GIT_TRACE2_EVENT` +environment variable or the `trace2.eventTarget` system or global config +setting. + +For example + +------------ +$ export GIT_TRACE2_EVENT=~/log.event +$ git version +git version 2.20.1.155.g426c96fcdb +------------ + +or + +------------ +$ git config --global trace2.eventTarget ~/log.event +$ git version +git version 2.20.1.155.g426c96fcdb +------------ + +yields + +------------ +$ cat ~/log.event +{"event":"version","sid":"sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.620713Z","file":"common-main.c","line":38,"evt":"1","exe":"2.20.1.155.g426c96fcdb"} +{"event":"start","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621027Z","file":"common-main.c","line":39,"t_abs":0.001173,"argv":["git","version"]} +{"event":"cmd_name","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621122Z","file":"git.c","line":432,"name":"version","hierarchy":"version"} +{"event":"exit","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621236Z","file":"git.c","line":662,"t_abs":0.001227,"code":0} +{"event":"atexit","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621268Z","file":"trace2/tr2_tgt_event.c","line":163,"t_abs":0.001265,"code":0} +------------ + +=== Enabling a Target + +To enable a target, set the corresponding environment variable or +system or global config value to one of the following: + +include::../trace2-target-values.txt[] + +If the target already exists and is a directory, the traces will be +written to files (one per process) underneath the given directory. They +will be named according to the last component of the SID (optionally +followed by a counter to avoid filename collisions). + +== Trace2 API + +All public Trace2 functions and macros are defined in `trace2.h` and +`trace2.c`. All public symbols are prefixed with `trace2_`. + +There are no public Trace2 data structures. + +The Trace2 code also defines a set of private functions and data types +in the `trace2/` directory. These symbols are prefixed with `tr2_` +and should only be used by functions in `trace2.c`. + +== Conventions for Public Functions and Macros + +The functions defined by the Trace2 API are declared and documented +in `trace2.h`. It defines the API functions and wrapper macros for +Trace2. + +Some functions have a `_fl()` suffix to indicate that they take `file` +and `line-number` arguments. + +Some functions have a `_va_fl()` suffix to indicate that they also +take a `va_list` argument. + +Some functions have a `_printf_fl()` suffix to indicate that they also +take a varargs argument. + +There are CPP wrapper macros and ifdefs to hide most of these details. +See `trace2.h` for more details. The following discussion will only +describe the simplified forms. + +== Public API + +All Trace2 API functions send a messsage to all of the active +Trace2 Targets. This section describes the set of available +messages. + +It helps to divide these functions into groups for discussion +purposes. + +=== Basic Command Messages + +These are concerned with the lifetime of the overall git process. + +`void trace2_initialize_clock()`:: + + Initialize the Trace2 start clock and nothing else. This should + be called at the very top of main() to capture the process start + time and reduce startup order dependencies. + +`void trace2_initialize()`:: + + Determines if any Trace2 Targets should be enabled and + initializes the Trace2 facility. This includes setting up the + Trace2 thread local storage (TLS). ++ +This function emits a "version" message containing the version of git +and the Trace2 protocol. ++ +This function should be called from `main()` as early as possible in +the life of the process after essential process initialization. + +`int trace2_is_enabled()`:: + + Returns 1 if Trace2 is enabled (at least one target is + active). + +`void trace2_cmd_start(int argc, const char **argv)`:: + + Emits a "start" message containing the process command line + arguments. + +`int trace2_cmd_exit(int exit_code)`:: + + Emits an "exit" message containing the process exit-code and + elapsed time. ++ +Returns the exit-code. + +`void trace2_cmd_error(const char *fmt, va_list ap)`:: + + Emits an "error" message containing a formatted error message. + +`void trace2_cmd_path(const char *pathname)`:: + + Emits a "cmd_path" message with the full pathname of the + current process. + +=== Command Detail Messages + +These are concerned with describing the specific Git command +after the command line, config, and environment are inspected. + +`void trace2_cmd_name(const char *name)`:: + + Emits a "cmd_name" message with the canonical name of the + command, for example "status" or "checkout". + +`void trace2_cmd_mode(const char *mode)`:: + + Emits a "cmd_mode" message with a qualifier name to further + describe the current git command. ++ +This message is intended to be used with git commands having multiple +major modes. For example, a "checkout" command can checkout a new +branch or it can checkout a single file, so the checkout code could +emit a cmd_mode message of "branch" or "file". + +`void trace2_cmd_alias(const char *alias, const char **argv_expansion)`:: + + Emits an "alias" message containing the alias used and the + argument expansion. + +`void trace2_def_param(const char *parameter, const char *value)`:: + + Emits a "def_param" message containing a key/value pair. ++ +This message is intended to report some global aspect of the current +command, such as a configuration setting or command line switch that +significantly affects program performance or behavior, such as +`core.abbrev`, `status.showUntrackedFiles`, or `--no-ahead-behind`. + +`void trace2_cmd_list_config()`:: + + Emits a "def_param" messages for "important" configuration + settings. ++ +The environment variable `GIT_TRACE2_CONFIG_PARAMS` or the `trace2.configParams` +config value can be set to a +list of patterns of important configuration settings, for example: +`core.*,remote.*.url`. This function will iterate over all config +settings and emit a "def_param" message for each match. + +`void trace2_cmd_set_config(const char *key, const char *value)`:: + + Emits a "def_param" message for a new or updated key/value + pair IF `key` is considered important. ++ +This is used to hook into `git_config_set()` and catch any +configuration changes and update a value previously reported by +`trace2_cmd_list_config()`. + +`void trace2_def_repo(struct repository *repo)`:: + + Registers a repository with the Trace2 layer. Assigns a + unique "repo-id" to `repo->trace2_repo_id`. ++ +Emits a "worktree" messages containing the repo-id and the worktree +pathname. ++ +Region and data messages (described later) may refer to this repo-id. ++ +The main/top-level repository will have repo-id value 1 (aka "r1"). ++ +The repo-id field is in anticipation of future in-proc submodule +repositories. + +=== Child Process Messages + +These are concerned with the various spawned child processes, +including shell scripts, git commands, editors, pagers, and hooks. + +`void trace2_child_start(struct child_process *cmd)`:: + + Emits a "child_start" message containing the "child-id", + "child-argv", and "child-classification". ++ +Before calling this, set `cmd->trace2_child_class` to a name +describing the type of child process, for example "editor". ++ +This function assigns a unique "child-id" to `cmd->trace2_child_id`. +This field is used later during the "child_exit" message to associate +it with the "child_start" message. ++ +This function should be called before spawning the child process. + +`void trace2_child_exit(struct child_proess *cmd, int child_exit_code)`:: + + Emits a "child_exit" message containing the "child-id", + the child's elapsed time and exit-code. ++ +The reported elapsed time includes the process creation overhead and +time spend waiting for it to exit, so it may be slightly longer than +the time reported by the child itself. ++ +This function should be called after reaping the child process. + +`int trace2_exec(const char *exe, const char **argv)`:: + + Emits a "exec" message containing the "exec-id" and the + argv of the new process. ++ +This function should be called before calling one of the `exec()` +variants, such as `execvp()`. ++ +This function returns a unique "exec-id". This value is used later +if the exec() fails and a "exec-result" message is necessary. + +`void trace2_exec_result(int exec_id, int error_code)`:: + + Emits a "exec_result" message containing the "exec-id" + and the error code. ++ +On Unix-based systems, `exec()` does not return if successful. +This message is used to indicate that the `exec()` failed and +that the current program is continuing. + +=== Git Thread Messages + +These messages are concerned with Git thread usage. + +`void trace2_thread_start(const char *thread_name)`:: + + Emits a "thread_start" message. ++ +The `thread_name` field should be a descriptive name, such as the +unique name of the thread-proc. A unique "thread-id" will be added +to the name to uniquely identify thread instances. ++ +Region and data messages (described later) may refer to this thread +name. ++ +This function must be called by the thread-proc of the new thread +(so that TLS data is properly initialized) and not by the caller +of `pthread_create()`. + +`void trace2_thread_exit()`:: + + Emits a "thread_exit" message containing the thread name + and the thread elapsed time. ++ +This function must be called by the thread-proc before it returns +(so that the coorect TLS data is used and cleaned up. It should +not be called by the caller of `pthread_join()`. + +=== Region and Data Messages + +These are concerned with recording performance data +over regions or spans of code. + +`void trace2_region_enter(const char *category, const char *label, const struct repository *repo)`:: + +`void trace2_region_enter_printf(const char *category, const char *label, const struct repository *repo, const char *fmt, ...)`:: + +`void trace2_region_enter_printf_va(const char *category, const char *label, const struct repository *repo, const char *fmt, va_list ap)`:: + + Emits a thread-relative "region_enter" message with optional + printf string. ++ +This function pushes a new region nesting stack level on the current +thread and starts a clock for the new stack frame. ++ +The `category` field is an arbitrary category name used to classify +regions by feature area, such as "status" or "index". At this time +it is only just printed along with the rest of the message. It may +be used in the future to filter messages. ++ +The `label` field is an arbitrary label used to describe the activity +being started, such as "read_recursive" or "do_read_index". ++ +The `repo` field, if set, will be used to get the "repo-id", so that +recursive oerations can be attributed to the correct repository. + +`void trace2_region_leave(const char *category, const char *label, const struct repository *repo)`:: + +`void trace2_region_leave_printf(const char *category, const char *label, const struct repository *repo, const char *fmt, ...)`:: + +`void trace2_region_leave_printf_va(const char *category, const char *label, const struct repository *repo, const char *fmt, va_list ap)`:: + + Emits a thread-relative "region_leave" message with optional + printf string. ++ +This function pops the region nesting stack on the current thread +and reports the elapsed time of the stack frame. ++ +The `category`, `label`, and `repo` fields are the same as above. +The `category` and `label` do not need to match the correpsonding +"region_enter" message, but it makes the data stream easier to +understand. + +`void trace2_data_string(const char *category, const struct repository *repo, const char *key, const char * value)`:: + +`void trace2_data_intmax(const char *category, const struct repository *repo, const char *key, intmax value)`:: + +`void trace2_data_json(const char *category, const struct repository *repo, const char *key, const struct json_writer *jw)`:: + + Emits a region- and thread-relative "data" or "data_json" message. ++ +This is a key/value pair message containing information about the +current thread, region stack, and repository. This could be used +to print the number of files in a directory during a multi-threaded +recursive tree walk. + +`void trace2_printf(const char *fmt, ...)`:: + +`void trace2_printf_va(const char *fmt, va_list ap)`:: + + Emits a region- and thread-relative "printf" message. + +== Trace2 Target Formats + +=== NORMAL Format + +Events are written as lines of the form: + +------------ +[<time> SP <filename>:<line> SP+] <event-name> [[SP] <event-message>] LF +------------ + +`<event-name>`:: + + is the event name. + +`<event-message>`:: + is a free-form printf message intended for human consumption. ++ +Note that this may contain embedded LF or CRLF characters that are +not escaped, so the event may spill across multiple lines. + +If `GIT_TRACE2_BRIEF` or `trace2.normalBrief` is true, the `time`, `filename`, +and `line` fields are omitted. + +This target is intended to be more of a summary (like GIT_TRACE) and +less detailed than the other targets. It ignores thread, region, and +data messages, for example. + +=== PERF Format + +Events are written as lines of the form: + +------------ +[<time> SP <filename>:<line> SP+ + BAR SP] d<depth> SP + BAR SP <thread-name> SP+ + BAR SP <event-name> SP+ + BAR SP [r<repo-id>] SP+ + BAR SP [<t_abs>] SP+ + BAR SP [<t_rel>] SP+ + BAR SP [<category>] SP+ + BAR SP DOTS* <perf-event-message> + LF +------------ + +`<depth>`:: + is the git process depth. This is the number of parent + git processes. A top-level git command has depth value "d0". + A child of it has depth value "d1". A second level child + has depth value "d2" and so on. + +`<thread-name>`:: + is a unique name for the thread. The primary thread + is called "main". Other thread names are of the form "th%d:%s" + and include a unique number and the name of the thread-proc. + +`<event-name>`:: + is the event name. + +`<repo-id>`:: + when present, is a number indicating the repository + in use. A `def_repo` event is emitted when a repository is + opened. This defines the repo-id and associated worktree. + Subsequent repo-specific events will reference this repo-id. ++ +Currently, this is always "r1" for the main repository. +This field is in anticipation of in-proc submodules in the future. + +`<t_abs>`:: + when present, is the absolute time in seconds since the + program started. + +`<t_rel>`:: + when present, is time in seconds relative to the start of + the current region. For a thread-exit event, it is the elapsed + time of the thread. + +`<category>`:: + is present on region and data events and is used to + indicate a broad category, such as "index" or "status". + +`<perf-event-message>`:: + is a free-form printf message intended for human consumption. + +------------ +15:33:33.532712 wt-status.c:2310 | d0 | main | region_enter | r1 | 0.126064 | | status | label:print +15:33:33.532712 wt-status.c:2331 | d0 | main | region_leave | r1 | 0.127568 | 0.001504 | status | label:print +------------ + +If `GIT_TRACE2_PERF_BRIEF` or `trace2.perfBrief` is true, the `time`, `file`, +and `line` fields are omitted. + +------------ +d0 | main | region_leave | r1 | 0.011717 | 0.009122 | index | label:preload +------------ + +The PERF target is intended for interactive performance analysis +during development and is quite noisy. + +=== EVENT Format + +Each event is a JSON-object containing multiple key/value pairs +written as a single line and followed by a LF. + +------------ +'{' <key> ':' <value> [',' <key> ':' <value>]* '}' LF +------------ + +Some key/value pairs are common to all events and some are +event-specific. + +==== Common Key/Value Pairs + +The following key/value pairs are common to all events: + +------------ +{ + "event":"version", + "sid":"20190408T191827.272759Z-H9b68c35f-P00003510", + "thread":"main", + "time":"2019-04-08T19:18:27.282761Z", + "file":"common-main.c", + "line":42, + ... +} +------------ + +`"event":<event>`:: + is the event name. + +`"sid":<sid>`:: + is the session-id. This is a unique string to identify the + process instance to allow all events emitted by a process to + be identified. A session-id is used instead of a PID because + PIDs are recycled by the OS. For child git processes, the + session-id is prepended with the session-id of the parent git + process to allow parent-child relationships to be identified + during post-processing. + +`"thread":<thread>`:: + is the thread name. + +`"time":<time>`:: + is the UTC time of the event. + +`"file":<filename>`:: + is source file generating the event. + +`"line":<line-number>`:: + is the integer source line number generating the event. + +`"repo":<repo-id>`:: + when present, is the integer repo-id as described previously. + +If `GIT_TRACE2_EVENT_BRIEF` or `trace2.eventBrief` is true, the `file` +and `line` fields are omitted from all events and the `time` field is +only present on the "start" and "atexit" events. + +==== Event-Specific Key/Value Pairs + +`"version"`:: + This event gives the version of the executable and the EVENT format. ++ +------------ +{ + "event":"version", + ... + "evt":"1", # EVENT format version + "exe":"2.20.1.155.g426c96fcdb" # git version +} +------------ + +`"start"`:: + This event contains the complete argv received by main(). ++ +------------ +{ + "event":"start", + ... + "t_abs":0.001227, # elapsed time in seconds + "argv":["git","version"] +} +------------ + +`"exit"`:: + This event is emitted when git calls `exit()`. ++ +------------ +{ + "event":"exit", + ... + "t_abs":0.001227, # elapsed time in seconds + "code":0 # exit code +} +------------ + +`"atexit"`:: + This event is emitted by the Trace2 `atexit` routine during + final shutdown. It should be the last event emitted by the + process. ++ +(The elapsed time reported here is greater than the time reported in +the "exit" event because it runs after all other atexit tasks have +completed.) ++ +------------ +{ + "event":"atexit", + ... + "t_abs":0.001227, # elapsed time in seconds + "code":0 # exit code +} +------------ + +`"signal"`:: + This event is emitted when the program is terminated by a user + signal. Depending on the platform, the signal event may + prevent the "atexit" event from being generated. ++ +------------ +{ + "event":"signal", + ... + "t_abs":0.001227, # elapsed time in seconds + "signo":13 # SIGTERM, SIGINT, etc. +} +------------ + +`"error"`:: + This event is emitted when one of the `error()`, `die()`, + or `usage()` functions are called. ++ +------------ +{ + "event":"error", + ... + "msg":"invalid option: --cahced", # formatted error message + "fmt":"invalid option: %s" # error format string +} +------------ ++ +The error event may be emitted more than once. The format string +allows post-processors to group errors by type without worrying +about specific error arguments. + +`"cmd_path"`:: + This event contains the discovered full path of the git + executable (on platforms that are configured to resolve it). ++ +------------ +{ + "event":"cmd_path", + ... + "path":"C:/work/gfw/git.exe" +} +------------ + +`"cmd_name"`:: + This event contains the command name for this git process + and the hierarchy of commands from parent git processes. ++ +------------ +{ + "event":"cmd_name", + ... + "name":"pack-objects", + "hierarchy":"push/pack-objects" +} +------------ ++ +Normally, the "name" field contains the canonical name of the +command. When a canonical name is not available, one of +these special values are used: ++ +------------ +"_query_" # "git --html-path" +"_run_dashed_" # when "git foo" tries to run "git-foo" +"_run_shell_alias_" # alias expansion to a shell command +"_run_git_alias_" # alias expansion to a git command +"_usage_" # usage error +------------ + +`"cmd_mode"`:: + This event, when present, describes the command variant This + event may be emitted more than once. ++ +------------ +{ + "event":"cmd_mode", + ... + "name":"branch" +} +------------ ++ +The "name" field is an arbitrary string to describe the command mode. +For example, checkout can checkout a branch or an individual file. +And these variations typically have different performance +characteristics that are not comparable. + +`"alias"`:: + This event is present when an alias is expanded. ++ +------------ +{ + "event":"alias", + ... + "alias":"l", # registered alias + "argv":["log","--graph"] # alias expansion +} +------------ + +`"child_start"`:: + This event describes a child process that is about to be + spawned. ++ +------------ +{ + "event":"child_start", + ... + "child_id":2, + "child_class":"?", + "use_shell":false, + "argv":["git","rev-list","--objects","--stdin","--not","--all","--quiet"] + + "hook_name":"<hook_name>" # present when child_class is "hook" + "cd":"<path>" # present when cd is required +} +------------ ++ +The "child_id" field can be used to match this child_start with the +corresponding child_exit event. ++ +The "child_class" field is a rough classification, such as "editor", +"pager", "transport/*", and "hook". Unclassified children are classified +with "?". + +`"child_exit"`:: + This event is generated after the current process has returned + from the waitpid() and collected the exit information from the + child. ++ +------------ +{ + "event":"child_exit", + ... + "child_id":2, + "pid":14708, # child PID + "code":0, # child exit-code + "t_rel":0.110605 # observed run-time of child process +} +------------ ++ +Note that the session-id of the child process is not available to +the current/spawning process, so the child's PID is reported here as +a hint for post-processing. (But it is only a hint because the child +proces may be a shell script which doesn't have a session-id.) ++ +Note that the `t_rel` field contains the observed run time in seconds +for the child process (starting before the fork/exec/spawn and +stopping after the waitpid() and includes OS process creation overhead). +So this time will be slightly larger than the atexit time reported by +the child process itself. + +`"exec"`:: + This event is generated before git attempts to `exec()` + another command rather than starting a child process. ++ +------------ +{ + "event":"exec", + ... + "exec_id":0, + "exe":"git", + "argv":["foo", "bar"] +} +------------ ++ +The "exec_id" field is a command-unique id and is only useful if the +`exec()` fails and a corresponding exec_result event is generated. + +`"exec_result"`:: + This event is generated if the `exec()` fails and control + returns to the current git command. ++ +------------ +{ + "event":"exec_result", + ... + "exec_id":0, + "code":1 # error code (errno) from exec() +} +------------ + +`"thread_start"`:: + This event is generated when a thread is started. It is + generated from *within* the new thread's thread-proc (for TLS + reasons). ++ +------------ +{ + "event":"thread_start", + ... + "thread":"th02:preload_thread" # thread name +} +------------ + +`"thread_exit"`:: + This event is generated when a thread exits. It is generated + from *within* the thread's thread-proc (for TLS reasons). ++ +------------ +{ + "event":"thread_exit", + ... + "thread":"th02:preload_thread", # thread name + "t_rel":0.007328 # thread elapsed time +} +------------ + +`"def_param"`:: + This event is generated to log a global parameter. ++ +------------ +{ + "event":"def_param", + ... + "param":"core.abbrev", + "value":"7" +} +------------ + +`"def_repo"`:: + This event defines a repo-id and associates it with the root + of the worktree. ++ +------------ +{ + "event":"def_repo", + ... + "repo":1, + "worktree":"/Users/jeffhost/work/gfw" +} +------------ ++ +As stated earlier, the repo-id is currently always 1, so there will +only be one def_repo event. Later, if in-proc submodules are +supported, a def_repo event should be emitted for each submodule +visited. + +`"region_enter"`:: + This event is generated when entering a region. ++ +------------ +{ + "event":"region_enter", + ... + "repo":1, # optional + "nesting":1, # current region stack depth + "category":"index", # optional + "label":"do_read_index", # optional + "msg":".git/index" # optional +} +------------ ++ +The `category` field may be used in a future enhancement to +do category-based filtering. ++ +`GIT_TRACE2_EVENT_NESTING` or `trace2.eventNesting` can be used to +filter deeply nested regions and data events. It defaults to "2". + +`"region_leave"`:: + This event is generated when leaving a region. ++ +------------ +{ + "event":"region_leave", + ... + "repo":1, # optional + "t_rel":0.002876, # time spent in region in seconds + "nesting":1, # region stack depth + "category":"index", # optional + "label":"do_read_index", # optional + "msg":".git/index" # optional +} +------------ + +`"data"`:: + This event is generated to log a thread- and region-local + key/value pair. ++ +------------ +{ + "event":"data", + ... + "repo":1, # optional + "t_abs":0.024107, # absolute elapsed time + "t_rel":0.001031, # elapsed time in region/thread + "nesting":2, # region stack depth + "category":"index", + "key":"read/cache_nr", + "value":"3552" +} +------------ ++ +The "value" field may be an integer or a string. + +`"data-json"`:: + This event is generated to log a pre-formatted JSON string + containing structured data. ++ +------------ +{ + "event":"data_json", + ... + "repo":1, # optional + "t_abs":0.015905, + "t_rel":0.015905, + "nesting":1, + "category":"process", + "key":"windows/ancestry", + "value":["bash.exe","bash.exe"] +} +------------ + +== Example Trace2 API Usage + +Here is a hypothetical usage of the Trace2 API showing the intended +usage (without worrying about the actual Git details). + +Initialization:: + + Initialization happens in `main()`. Behind the scenes, an + `atexit` and `signal` handler are registered. ++ +---------------- +int main(int argc, const char **argv) +{ + int exit_code; + + trace2_initialize(); + trace2_cmd_start(argv); + + exit_code = cmd_main(argc, argv); + + trace2_cmd_exit(exit_code); + + return exit_code; +} +---------------- + +Command Details:: + + After the basics are established, additional command + information can be sent to Trace2 as it is discovered. ++ +---------------- +int cmd_checkout(int argc, const char **argv) +{ + trace2_cmd_name("checkout"); + trace2_cmd_mode("branch"); + trace2_def_repo(the_repository); + + // emit "def_param" messages for "interesting" config settings. + trace2_cmd_list_config(); + + if (do_something()) + trace2_cmd_error("Path '%s': cannot do something", path); + + return 0; +} +---------------- + +Child Processes:: + + Wrap code spawning child processes. ++ +---------------- +void run_child(...) +{ + int child_exit_code; + struct child_process cmd = CHILD_PROCESS_INIT; + ... + cmd.trace2_child_class = "editor"; + + trace2_child_start(&cmd); + child_exit_code = spawn_child_and_wait_for_it(); + trace2_child_exit(&cmd, child_exit_code); +} +---------------- ++ +For example, the following fetch command spawned ssh, index-pack, +rev-list, and gc. This example also shows that fetch took +5.199 seconds and of that 4.932 was in ssh. ++ +---------------- +$ export GIT_TRACE2_BRIEF=1 +$ export GIT_TRACE2=~/log.normal +$ git fetch origin +... +---------------- ++ +---------------- +$ cat ~/log.normal +version 2.20.1.vfs.1.1.47.g534dbe1ad1 +start git fetch origin +worktree /Users/jeffhost/work/gfw +cmd_name fetch (fetch) +child_start[0] ssh git@github.com ... +child_start[1] git index-pack ... +... (Trace2 events from child processes omitted) +child_exit[1] pid:14707 code:0 elapsed:0.076353 +child_exit[0] pid:14706 code:0 elapsed:4.931869 +child_start[2] git rev-list ... +... (Trace2 events from child process omitted) +child_exit[2] pid:14708 code:0 elapsed:0.110605 +child_start[3] git gc --auto +... (Trace2 events from child process omitted) +child_exit[3] pid:14709 code:0 elapsed:0.006240 +exit elapsed:5.198503 code:0 +atexit elapsed:5.198541 code:0 +---------------- ++ +When a git process is a (direct or indirect) child of another +git process, it inherits Trace2 context information. This +allows the child to print the command hierarchy. This example +shows gc as child[3] of fetch. When the gc process reports +its name as "gc", it also reports the hierarchy as "fetch/gc". +(In this example, trace2 messages from the child process is +indented for clarity.) ++ +---------------- +$ export GIT_TRACE2_BRIEF=1 +$ export GIT_TRACE2=~/log.normal +$ git fetch origin +... +---------------- ++ +---------------- +$ cat ~/log.normal +version 2.20.1.160.g5676107ecd.dirty +start git fetch official +worktree /Users/jeffhost/work/gfw +cmd_name fetch (fetch) +... +child_start[3] git gc --auto + version 2.20.1.160.g5676107ecd.dirty + start /Users/jeffhost/work/gfw/git gc --auto + worktree /Users/jeffhost/work/gfw + cmd_name gc (fetch/gc) + exit elapsed:0.001959 code:0 + atexit elapsed:0.001997 code:0 +child_exit[3] pid:20303 code:0 elapsed:0.007564 +exit elapsed:3.868938 code:0 +atexit elapsed:3.868970 code:0 +---------------- + +Regions:: + + Regions can be use to time an interesting section of code. ++ +---------------- +void wt_status_collect(struct wt_status *s) +{ + trace2_region_enter("status", "worktrees", s->repo); + wt_status_collect_changes_worktree(s); + trace2_region_leave("status", "worktrees", s->repo); + + trace2_region_enter("status", "index", s->repo); + wt_status_collect_changes_index(s); + trace2_region_leave("status", "index", s->repo); + + trace2_region_enter("status", "untracked", s->repo); + wt_status_collect_untracked(s); + trace2_region_leave("status", "untracked", s->repo); +} + +void wt_status_print(struct wt_status *s) +{ + trace2_region_enter("status", "print", s->repo); + switch (s->status_format) { + ... + } + trace2_region_leave("status", "print", s->repo); +} +---------------- ++ +In this example, scanning for untracked files ran from +0.012568 to ++0.027149 (since the process started) and took 0.014581 seconds. ++ +---------------- +$ export GIT_TRACE2_PERF_BRIEF=1 +$ export GIT_TRACE2_PERF=~/log.perf +$ git status +... + +$ cat ~/log.perf +d0 | main | version | | | | | 2.20.1.160.g5676107ecd.dirty +d0 | main | start | | 0.001173 | | | git status +d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw +d0 | main | cmd_name | | | | | status (status) +... +d0 | main | region_enter | r1 | 0.010988 | | status | label:worktrees +d0 | main | region_leave | r1 | 0.011236 | 0.000248 | status | label:worktrees +d0 | main | region_enter | r1 | 0.011260 | | status | label:index +d0 | main | region_leave | r1 | 0.012542 | 0.001282 | status | label:index +d0 | main | region_enter | r1 | 0.012568 | | status | label:untracked +d0 | main | region_leave | r1 | 0.027149 | 0.014581 | status | label:untracked +d0 | main | region_enter | r1 | 0.027411 | | status | label:print +d0 | main | region_leave | r1 | 0.028741 | 0.001330 | status | label:print +d0 | main | exit | | 0.028778 | | | code:0 +d0 | main | atexit | | 0.028809 | | | code:0 +---------------- ++ +Regions may be nested. This causes messages to be indented in the +PERF target, for example. +Elapsed times are relative to the start of the correpsonding nesting +level as expected. For example, if we add region message to: ++ +---------------- +static enum path_treatment read_directory_recursive(struct dir_struct *dir, + struct index_state *istate, const char *base, int baselen, + struct untracked_cache_dir *untracked, int check_only, + int stop_at_first_file, const struct pathspec *pathspec) +{ + enum path_treatment state, subdir_state, dir_state = path_none; + + trace2_region_enter_printf("dir", "read_recursive", NULL, "%.*s", baselen, base); + ... + trace2_region_leave_printf("dir", "read_recursive", NULL, "%.*s", baselen, base); + return dir_state; +} +---------------- ++ +We can further investigate the time spent scanning for untracked files. ++ +---------------- +$ export GIT_TRACE2_PERF_BRIEF=1 +$ export GIT_TRACE2_PERF=~/log.perf +$ git status +... +$ cat ~/log.perf +d0 | main | version | | | | | 2.20.1.162.gb4ccea44db.dirty +d0 | main | start | | 0.001173 | | | git status +d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw +d0 | main | cmd_name | | | | | status (status) +... +d0 | main | region_enter | r1 | 0.015047 | | status | label:untracked +d0 | main | region_enter | | 0.015132 | | dir | ..label:read_recursive +d0 | main | region_enter | | 0.016341 | | dir | ....label:read_recursive vcs-svn/ +d0 | main | region_leave | | 0.016422 | 0.000081 | dir | ....label:read_recursive vcs-svn/ +d0 | main | region_enter | | 0.016446 | | dir | ....label:read_recursive xdiff/ +d0 | main | region_leave | | 0.016522 | 0.000076 | dir | ....label:read_recursive xdiff/ +d0 | main | region_enter | | 0.016612 | | dir | ....label:read_recursive git-gui/ +d0 | main | region_enter | | 0.016698 | | dir | ......label:read_recursive git-gui/po/ +d0 | main | region_enter | | 0.016810 | | dir | ........label:read_recursive git-gui/po/glossary/ +d0 | main | region_leave | | 0.016863 | 0.000053 | dir | ........label:read_recursive git-gui/po/glossary/ +... +d0 | main | region_enter | | 0.031876 | | dir | ....label:read_recursive builtin/ +d0 | main | region_leave | | 0.032270 | 0.000394 | dir | ....label:read_recursive builtin/ +d0 | main | region_leave | | 0.032414 | 0.017282 | dir | ..label:read_recursive +d0 | main | region_leave | r1 | 0.032454 | 0.017407 | status | label:untracked +... +d0 | main | exit | | 0.034279 | | | code:0 +d0 | main | atexit | | 0.034322 | | | code:0 +---------------- ++ +Trace2 regions are similar to the existing trace_performance_enter() +and trace_performance_leave() routines, but are thread safe and +maintain per-thread stacks of timers. + +Data Messages:: + + Data messages added to a region. ++ +---------------- +int read_index_from(struct index_state *istate, const char *path, + const char *gitdir) +{ + trace2_region_enter_printf("index", "do_read_index", the_repository, "%s", path); + + ... + + trace2_data_intmax("index", the_repository, "read/version", istate->version); + trace2_data_intmax("index", the_repository, "read/cache_nr", istate->cache_nr); + + trace2_region_leave_printf("index", "do_read_index", the_repository, "%s", path); +} +---------------- ++ +This example shows that the index contained 3552 entries. ++ +---------------- +$ export GIT_TRACE2_PERF_BRIEF=1 +$ export GIT_TRACE2_PERF=~/log.perf +$ git status +... +$ cat ~/log.perf +d0 | main | version | | | | | 2.20.1.156.gf9916ae094.dirty +d0 | main | start | | 0.001173 | | | git status +d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw +d0 | main | cmd_name | | | | | status (status) +d0 | main | region_enter | r1 | 0.001791 | | index | label:do_read_index .git/index +d0 | main | data | r1 | 0.002494 | 0.000703 | index | ..read/version:2 +d0 | main | data | r1 | 0.002520 | 0.000729 | index | ..read/cache_nr:3552 +d0 | main | region_leave | r1 | 0.002539 | 0.000748 | index | label:do_read_index .git/index +... +---------------- + +Thread Events:: + + Thread messages added to a thread-proc. ++ +For example, the multithreaded preload-index code can be +instrumented with a region around the thread pool and then +per-thread start and exit events within the threadproc. ++ +---------------- +static void *preload_thread(void *_data) +{ + // start the per-thread clock and emit a message. + trace2_thread_start("preload_thread"); + + // report which chunk of the array this thread was assigned. + trace2_data_intmax("index", the_repository, "offset", p->offset); + trace2_data_intmax("index", the_repository, "count", nr); + + do { + ... + } while (--nr > 0); + ... + + // report elapsed time taken by this thread. + trace2_thread_exit(); + return NULL; +} + +void preload_index(struct index_state *index, + const struct pathspec *pathspec, + unsigned int refresh_flags) +{ + trace2_region_enter("index", "preload", the_repository); + + for (i = 0; i < threads; i++) { + ... /* create thread */ + } + + for (i = 0; i < threads; i++) { + ... /* join thread */ + } + + trace2_region_leave("index", "preload", the_repository); +} +---------------- ++ +In this example preload_index() was executed by the `main` thread +and started the `preload` region. Seven threads, named +`th01:preload_thread` through `th07:preload_thread`, were started. +Events from each thread are atomically appended to the shared target +stream as they occur so they may appear in random order with respect +other threads. Finally, the main thread waits for the threads to +finish and leaves the region. ++ +Data events are tagged with the active thread name. They are used +to report the per-thread parameters. ++ +---------------- +$ export GIT_TRACE2_PERF_BRIEF=1 +$ export GIT_TRACE2_PERF=~/log.perf +$ git status +... +$ cat ~/log.perf +... +d0 | main | region_enter | r1 | 0.002595 | | index | label:preload +d0 | th01:preload_thread | thread_start | | 0.002699 | | | +d0 | th02:preload_thread | thread_start | | 0.002721 | | | +d0 | th01:preload_thread | data | r1 | 0.002736 | 0.000037 | index | offset:0 +d0 | th02:preload_thread | data | r1 | 0.002751 | 0.000030 | index | offset:2032 +d0 | th03:preload_thread | thread_start | | 0.002711 | | | +d0 | th06:preload_thread | thread_start | | 0.002739 | | | +d0 | th01:preload_thread | data | r1 | 0.002766 | 0.000067 | index | count:508 +d0 | th06:preload_thread | data | r1 | 0.002856 | 0.000117 | index | offset:2540 +d0 | th03:preload_thread | data | r1 | 0.002824 | 0.000113 | index | offset:1016 +d0 | th04:preload_thread | thread_start | | 0.002710 | | | +d0 | th02:preload_thread | data | r1 | 0.002779 | 0.000058 | index | count:508 +d0 | th06:preload_thread | data | r1 | 0.002966 | 0.000227 | index | count:508 +d0 | th07:preload_thread | thread_start | | 0.002741 | | | +d0 | th07:preload_thread | data | r1 | 0.003017 | 0.000276 | index | offset:3048 +d0 | th05:preload_thread | thread_start | | 0.002712 | | | +d0 | th05:preload_thread | data | r1 | 0.003067 | 0.000355 | index | offset:1524 +d0 | th05:preload_thread | data | r1 | 0.003090 | 0.000378 | index | count:508 +d0 | th07:preload_thread | data | r1 | 0.003037 | 0.000296 | index | count:504 +d0 | th03:preload_thread | data | r1 | 0.002971 | 0.000260 | index | count:508 +d0 | th04:preload_thread | data | r1 | 0.002983 | 0.000273 | index | offset:508 +d0 | th04:preload_thread | data | r1 | 0.007311 | 0.004601 | index | count:508 +d0 | th05:preload_thread | thread_exit | | 0.008781 | 0.006069 | | +d0 | th01:preload_thread | thread_exit | | 0.009561 | 0.006862 | | +d0 | th03:preload_thread | thread_exit | | 0.009742 | 0.007031 | | +d0 | th06:preload_thread | thread_exit | | 0.009820 | 0.007081 | | +d0 | th02:preload_thread | thread_exit | | 0.010274 | 0.007553 | | +d0 | th07:preload_thread | thread_exit | | 0.010477 | 0.007736 | | +d0 | th04:preload_thread | thread_exit | | 0.011657 | 0.008947 | | +d0 | main | region_leave | r1 | 0.011717 | 0.009122 | index | label:preload +... +d0 | main | exit | | 0.029996 | | | code:0 +d0 | main | atexit | | 0.030027 | | | code:0 +---------------- ++ +In this example, the preload region took 0.009122 seconds. The 7 threads +took between 0.006069 and 0.008947 seconds to work on their portion of +the index. Thread "th01" worked on 508 items at offset 0. Thread "th02" +worked on 508 items at offset 2032. Thread "th04" worked on 508 itemts +at offset 508. ++ +This example also shows that thread names are assigned in a racy manner +as each thread starts and allocates TLS storage. + +== Future Work + +=== Relationship to the Existing Trace Api (api-trace.txt) + +There are a few issues to resolve before we can completely +switch to Trace2. + +* Updating existing tests that assume GIT_TRACE format messages. + +* How to best handle custom GIT_TRACE_<key> messages? + +** The GIT_TRACE_<key> mechanism allows each <key> to write to a +different file (in addition to just stderr). + +** Do we want to maintain that ability or simply write to the existing +Trace2 targets (and convert <key> to a "category"). diff --git a/Documentation/technical/commit-graph-format.txt b/Documentation/technical/commit-graph-format.txt index cc0474ba3e..16452a0504 100644 --- a/Documentation/technical/commit-graph-format.txt +++ b/Documentation/technical/commit-graph-format.txt @@ -76,7 +76,7 @@ CHUNK DATA: of the ith commit. Stores value 0x7000000 if no parent in that position. If there are more than two parents, the second value has its most-significant bit on and the other bits store an array - position into the Large Edge List chunk. + position into the Extra Edge List chunk. * The next 8 bytes store the generation number of the commit and the commit time in seconds since EPOCH. The generation number uses the higher 30 bits of the first 4 bytes, while the commit @@ -84,7 +84,7 @@ CHUNK DATA: 2 bits of the lowest byte, storing the 33rd and 34th bit of the commit time. - Large Edge List (ID: {'E', 'D', 'G', 'E'}) [Optional] + Extra Edge List (ID: {'E', 'D', 'G', 'E'}) [Optional] This list of 4-byte values store the second through nth parents for all octopus merges. The second parent value in the commit data stores an array position within this list along with the most-significant bit diff --git a/Documentation/technical/commit-graph.txt b/Documentation/technical/commit-graph.txt index 7805b0968c..fb53341d5e 100644 --- a/Documentation/technical/commit-graph.txt +++ b/Documentation/technical/commit-graph.txt @@ -127,23 +127,6 @@ Design Details helpful for these clones, anyway. The commit-graph will not be read or written when shallow commits are present. -Future Work ------------ - -- After computing and storing generation numbers, we must make graph - walks aware of generation numbers to gain the performance benefits they - enable. This will mostly be accomplished by swapping a commit-date-ordered - priority queue with one ordered by generation number. The following - operations are important candidates: - - - 'log --topo-order' - - 'tag --merged' - -- A server could provide a commit-graph file as part of the network protocol - to avoid extra calculations by clients. This feature is only of benefit if - the user is willing to trust the file, because verifying the file is correct - is as hard as computing it from scratch. - Related Links ------------- [0] https://bugs.chromium.org/p/git/issues/detail?id=8 diff --git a/Documentation/technical/directory-rename-detection.txt b/Documentation/technical/directory-rename-detection.txt index 1c0086e287..844629c8c4 100644 --- a/Documentation/technical/directory-rename-detection.txt +++ b/Documentation/technical/directory-rename-detection.txt @@ -20,8 +20,8 @@ More interesting possibilities exist, though, such as: * one side of history renames x -> z, and the other renames some file to x/e, causing the need for the merge to do a transitive rename. - * one side of history renames x -> z, but also renames all files within - x. For example, x/a -> z/alpha, x/b -> z/bravo, etc. + * one side of history renames x -> z, but also renames all files within x. + For example, x/a -> z/alpha, x/b -> z/bravo, etc. * both 'x' and 'y' being merged into a single directory 'z', with a directory rename being detected for both x->z and y->z. diff --git a/Documentation/technical/pack-protocol.txt b/Documentation/technical/pack-protocol.txt index 6ac774d5f6..c73e72de0e 100644 --- a/Documentation/technical/pack-protocol.txt +++ b/Documentation/technical/pack-protocol.txt @@ -22,6 +22,16 @@ protocol-common.txt. When the grammar indicate `PKT-LINE(...)`, unless otherwise noted the usual pkt-line LF rules apply: the sender SHOULD include a LF, but the receiver MUST NOT complain if it is not present. +An error packet is a special pkt-line that contains an error string. + +---- + error-line = PKT-LINE("ERR" SP explanation-text) +---- + +Throughout the protocol, where `PKT-LINE(...)` is expected, an error packet MAY +be sent. Once this packet is sent by a client or a server, the data transfer +process defined in this protocol is terminated. + Transports ---------- There are three transports over which the packfile protocol is @@ -89,13 +99,6 @@ process on the server side over the Git protocol is this: "0039git-upload-pack /schacon/gitbook.git\0host=example.com\0" | nc -v example.com 9418 -If the server refuses the request for some reasons, it could abort -gracefully with an error message. - ----- - error-line = PKT-LINE("ERR" SP explanation-text) ----- - SSH Transport ------------- @@ -398,12 +401,11 @@ from the client). Then the server will start sending its packfile data. ---- - server-response = *ack_multi ack / nak / error-line + server-response = *ack_multi ack / nak ack_multi = PKT-LINE("ACK" SP obj-id ack_status) ack_status = "continue" / "common" / "ready" ack = PKT-LINE("ACK" SP obj-id) nak = PKT-LINE("NAK") - error-line = PKT-LINE("ERR" SP explanation-text) ---- A simple clone may look like this (with no 'have' lines): @@ -655,14 +657,14 @@ can be rejected. An example client/server communication might look like this: ---- - S: 007c74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/local\0report-status delete-refs ofs-delta\n + S: 006274730d410fcb6603ace96f1dc55ea6196122532d refs/heads/local\0report-status delete-refs ofs-delta\n S: 003e7d1665144a3a975c05f1f43902ddaf084e784dbe refs/heads/debug\n S: 003f74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/master\n - S: 003f74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/team\n + S: 003d74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/team\n S: 0000 - C: 003e7d1665144a3a975c05f1f43902ddaf084e784dbe 74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/debug\n - C: 003e74730d410fcb6603ace96f1dc55ea6196122532d 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a refs/heads/master\n + C: 00677d1665144a3a975c05f1f43902ddaf084e784dbe 74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/debug\n + C: 006874730d410fcb6603ace96f1dc55ea6196122532d 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a refs/heads/master\n C: 0000 C: [PACKDATA] diff --git a/Documentation/technical/partial-clone.txt b/Documentation/technical/partial-clone.txt index 1ef66bd788..896c7b3878 100644 --- a/Documentation/technical/partial-clone.txt +++ b/Documentation/technical/partial-clone.txt @@ -114,7 +114,7 @@ their "<name>.pack" and "<name>.idx" files. that it has, either because the local repository has that object in one of its promisor packfiles, or because another promisor object refers to it. + -When Git encounters a missing object, Git can see if it a promisor object +When Git encounters a missing object, Git can see if it is a promisor object and handle it appropriately. If not, Git can report a corruption. + This means that there is no need for the client to explicitly maintain an diff --git a/Documentation/technical/protocol-capabilities.txt b/Documentation/technical/protocol-capabilities.txt index 332d209b58..2b267c0da6 100644 --- a/Documentation/technical/protocol-capabilities.txt +++ b/Documentation/technical/protocol-capabilities.txt @@ -1,6 +1,10 @@ Git Protocol Capabilities ========================= +NOTE: this document describes capabilities for versions 0 and 1 of the pack +protocol. For version 2, please refer to the link:protocol-v2.html[protocol-v2] +doc. + Servers SHOULD support all capabilities defined in this document. On the very first line of the initial server response of either @@ -172,6 +176,20 @@ agent strings are purely informative for statistics and debugging purposes, and MUST NOT be used to programmatically assume the presence or absence of particular features. +symref +------ + +This parameterized capability is used to inform the receiver which symbolic ref +points to which ref; for example, "symref=HEAD:refs/heads/master" tells the +receiver that HEAD points to master. This capability can be repeated to +represent multiple symrefs. + +Servers SHOULD include this capability for the HEAD symref if it is one of the +refs being sent. + +Clients MAY use the parameters from this capability to select the proper initial +branch when cloning a repository. + shallow ------- diff --git a/Documentation/technical/protocol-v2.txt b/Documentation/technical/protocol-v2.txt index 09e4e0273f..03264c7d9a 100644 --- a/Documentation/technical/protocol-v2.txt +++ b/Documentation/technical/protocol-v2.txt @@ -1,5 +1,5 @@ - Git Wire Protocol, Version 2 -============================== +Git Wire Protocol, Version 2 +============================ This document presents a specification for a version 2 of Git's wire protocol. Protocol v2 will improve upon v1 in the following ways: @@ -22,8 +22,8 @@ will be commands which a client can request be executed. Once a command has completed, a client can reuse the connection and request that other commands be executed. - Packet-Line Framing ---------------------- +Packet-Line Framing +------------------- All communication is done using packet-line framing, just as in v1. See `Documentation/technical/pack-protocol.txt` and @@ -34,8 +34,8 @@ In protocol v2 these special packets will have the following semantics: * '0000' Flush Packet (flush-pkt) - indicates the end of a message * '0001' Delimiter Packet (delim-pkt) - separates sections of a message - Initial Client Request ------------------------- +Initial Client Request +---------------------- In general a client can request to speak protocol v2 by sending `version=2` through the respective side-channel for the transport being @@ -43,22 +43,22 @@ used which inevitably sets `GIT_PROTOCOL`. More information can be found in `pack-protocol.txt` and `http-protocol.txt`. In all cases the response from the server is the capability advertisement. - Git Transport -~~~~~~~~~~~~~~~ +Git Transport +~~~~~~~~~~~~~ When using the git:// transport, you can request to use protocol v2 by sending "version=2" as an extra parameter: 003egit-upload-pack /project.git\0host=myserver.com\0\0version=2\0 - SSH and File Transport -~~~~~~~~~~~~~~~~~~~~~~~~ +SSH and File Transport +~~~~~~~~~~~~~~~~~~~~~~ When using either the ssh:// or file:// transport, the GIT_PROTOCOL environment variable must be set explicitly to include "version=2". - HTTP Transport -~~~~~~~~~~~~~~~~ +HTTP Transport +~~~~~~~~~~~~~~ When using the http:// or https:// transport a client makes a "smart" info/refs request as described in `http-protocol.txt` and requests that @@ -79,8 +79,8 @@ A v2 server would reply: Subsequent requests are then made directly to the service `$GIT_URL/git-upload-pack`. (This works the same for git-receive-pack). - Capability Advertisement --------------------------- +Capability Advertisement +------------------------ A server which decides to communicate (based on a request from a client) using protocol version 2, notifies the client by sending a version string @@ -101,8 +101,8 @@ to be executed by the client. key = 1*(ALPHA | DIGIT | "-_") value = 1*(ALPHA | DIGIT | " -_.,?\/{}[]()<>!@#$%^&*+=:;") - Command Request ------------------ +Command Request +--------------- After receiving the capability advertisement, a client can then issue a request to select the command it wants with any particular capabilities @@ -137,8 +137,8 @@ command be executed or can terminate the connection. A client may optionally send an empty request consisting of just a flush-pkt to indicate that no more requests will be made. - Capabilities --------------- +Capabilities +------------ There are two different types of capabilities: normal capabilities, which can be used to to convey information or alter the behavior of a @@ -153,8 +153,8 @@ management on the server side in order to function correctly. This permits simple round-robin load-balancing on the server side, without needing to worry about state management. - agent -~~~~~~~ +agent +~~~~~ The server can advertise the `agent` capability with a value `X` (in the form `agent=X`) to notify the client that the server is running version @@ -168,8 +168,8 @@ printable ASCII characters except space (i.e., the byte range 32 < x < and debugging purposes, and MUST NOT be used to programmatically assume the presence or absence of particular features. - ls-refs -~~~~~~~~~ +ls-refs +~~~~~~~ `ls-refs` is the command used to request a reference advertisement in v2. Unlike the current reference advertisement, ls-refs takes in arguments @@ -199,8 +199,8 @@ The output of ls-refs is as follows: symref = "symref-target:" symref-target peeled = "peeled:" obj-id - fetch -~~~~~~~ +fetch +~~~~~ `fetch` is the command used to fetch a packfile in v2. It can be looked at as a modified version of the v1 fetch where the ref-advertisement is @@ -296,7 +296,13 @@ included in the client's request: Request that various objects from the packfile be omitted using one of several filtering techniques. These are intended for use with partial clone and partial fetch operations. See - `rev-list` for possible "filter-spec" values. + `rev-list` for possible "filter-spec" values. When communicating + with other processes, senders SHOULD translate scaled integers + (e.g. "1k") into a fully-expanded form (e.g. "1024") to aid + interoperability with older receivers that may not understand + newly-invented scaling suffixes. However, receivers SHOULD + accept the following suffixes: 'k', 'm', and 'g' for 1024, + 1048576, and 1073741824, respectively. If the 'ref-in-want' feature is advertised, the following argument can be included in the client's request as well as the potential addition of @@ -307,6 +313,16 @@ the 'wanted-refs' section in the server's response as explained below. particular ref, where <ref> is the full name of a ref on the server. +If the 'sideband-all' feature is advertised, the following argument can be +included in the client's request: + + sideband-all + Instruct the server to send the whole response multiplexed, not just + the packfile section. All non-flush and non-delim PKT-LINE in the + response (not only in the packfile section) will then start with a byte + indicating its sideband (1, 2, or 3), and the server may send "0005\2" + (a PKT-LINE of sideband 2 with no payload) as a keepalive packet. + The response of `fetch` is broken into a number of sections separated by delimiter packets (0001), with each section beginning with its section header. @@ -428,8 +444,8 @@ header. 2 - progress messages 3 - fatal error message just before stream aborts - server-option -~~~~~~~~~~~~~~~ +server-option +~~~~~~~~~~~~~ If advertised, indicates that any number of server specific options can be included in a request. This is done by sending each option as a |