4 files changed, 134 insertions, 11 deletions
diff --git a/Documentation/technical/api-parse-options.txt b/Documentation/technical/api-parse-options.txt
index acfd5dc1d8..c2a5e42914 100644
--- a/Documentation/technical/api-parse-options.txt
+++ b/Documentation/technical/api-parse-options.txt
@@ -8,7 +8,8 @@ Basics
 ------
 
 The argument vector `argv[]` may usually contain mandatory or optional
-'non-option arguments', e.g. a filename or a branch, and 'options'.
+'non-option arguments', e.g. a filename or a branch, 'options', and
+'subcommands'.
 Options are optional arguments that start with a dash and
 that allow to change the behavior of a command.
 
@@ -48,6 +49,33 @@ The parse-options API allows:
   option, e.g. `-a -b --option -- --this-is-a-file` indicates that
   `--this-is-a-file` must not be processed as an option.
 
+Subcommands are special in a couple of ways:
+
+* Subcommands only have long form, and they have no double dash prefix, no
+  negated form, and no description, and they don't take any arguments, and
+  can't be abbreviated.
+
+* There must be exactly one subcommand among the arguments, or zero if the
+  command has a default operation mode.
+
+* All arguments following the subcommand are considered to be arguments of
+  the subcommand, and, conversely, arguments meant for the subcommand may
+  not preceed the subcommand.
+
+Therefore, if the options array contains at least one subcommand and
+`parse_options()` encounters the first dashless argument, it will either:
+
+* stop and return, if that dashless argument is a known subcommand, setting
+  `value` to the function pointer associated with that subcommand, storing
+  the name of the subcommand in argv[0], and leaving the rest of the
+  arguments unprocessed, or
+
+* stop and return, if it was invoked with the `PARSE_OPT_SUBCOMMAND_OPTIONAL`
+  flag and that dashless argument doesn't match any subcommands, leaving
+  `value` unchanged and the rest of the arguments unprocessed, or
+
+* show error and usage, and abort.
+
 Steps to parse options
 ----------------------
 
@@ -90,8 +118,8 @@ Flags are the bitwise-or of:
 	Keep the first argument, which contains the program name.  It's
 	removed from argv[] by default.
 
-`PARSE_OPT_KEEP_UNKNOWN`::
-	Keep unknown arguments instead of erroring out.  This doesn't
+`PARSE_OPT_KEEP_UNKNOWN_OPT`::
+	Keep unknown options instead of erroring out.  This doesn't
 	work for all combinations of arguments as users might expect
 	it to do.  E.g. if the first argument in `--unknown --known`
 	takes a value (which we can't know), the second one is
@@ -101,6 +129,8 @@ Flags are the bitwise-or of:
 	non-option, not as a value belonging to the unknown option,
 	the parser early.  That's why parse_options() errors out if
 	both options are set.
+	Note that non-option arguments are always kept, even without
+	this flag.
 
 `PARSE_OPT_NO_INTERNAL_HELP`::
 	By default, parse_options() handles `-h`, `--help` and
@@ -108,6 +138,13 @@ Flags are the bitwise-or of:
 	turns it off and allows one to add custom handlers for these
 	options, or to just leave them unknown.
 
+`PARSE_OPT_SUBCOMMAND_OPTIONAL`::
+	Don't error out when no subcommand is specified.
+
+Note that `PARSE_OPT_STOP_AT_NON_OPTION` is incompatible with subcommands;
+while `PARSE_OPT_KEEP_DASHDASH` and `PARSE_OPT_KEEP_UNKNOWN_OPT` can only be
+used with subcommands when combined with `PARSE_OPT_SUBCOMMAND_OPTIONAL`.
+
 Data Structure
 --------------
 
@@ -236,10 +273,14 @@ There are some macros to easily define options:
 `OPT_CMDMODE(short, long, &int_var, description, enum_val)`::
 	Define an "operation mode" option, only one of which in the same
 	group of "operating mode" options that share the same `int_var`
-	can be given by the user. `enum_val` is set to `int_var` when the
+	can be given by the user. `int_var` is set to `enum_val` when the
 	option is used, but an error is reported if other "operating mode"
 	option has already set its value to the same `int_var`.
+	In new commands consider using subcommands instead.
 
+`OPT_SUBCOMMAND(long, &fn_ptr, subcommand_fn)`::
+	Define a subcommand.  `subcommand_fn` is put into `fn_ptr` when
+	this subcommand is used.
 
 The last element of the array must be `OPT_END()`.
 
diff --git a/Documentation/technical/api-trace2.txt b/Documentation/technical/api-trace2.txt
index 77a150b30e..2afa28bb5a 100644
--- a/Documentation/technical/api-trace2.txt
+++ b/Documentation/technical/api-trace2.txt
@@ -717,6 +717,7 @@ The "exec_id" field is a command-unique id and is only useful if the
 {
 	"event":"def_param",
 	...
+	"scope":"global",
 	"param":"core.abbrev",
 	"value":"7"
 }
@@ -1207,6 +1208,45 @@ at offset 508.
 This example also shows that thread names are assigned in a racy manner
 as each thread starts and allocates TLS storage.
 
+Config (def param) Events::
+
+	  Dump "interesting" config values to trace2 log.
++
+We can optionally emit configuration events, see
+`trace2.configparams` in linkgit:git-config[1] for how to enable
+it.
++
+----------------
+$ git config --system color.ui never
+$ git config --global color.ui always
+$ git config --local color.ui auto
+$ git config --list --show-scope | grep 'color.ui'
+system  color.ui=never
+global  color.ui=always
+local   color.ui=auto
+----------------
++
+Then, mark the config `color.ui` as "interesting" config with
+`GIT_TRACE2_CONFIG_PARAMS`:
++
+----------------
+$ export GIT_TRACE2_PERF_BRIEF=1
+$ export GIT_TRACE2_PERF=~/log.perf
+$ export GIT_TRACE2_CONFIG_PARAMS=color.ui
+$ git version
+...
+$ cat ~/log.perf
+d0 | main                     | version      |     |           |           |              | ...
+d0 | main                     | start        |     |  0.001642 |           |              | /usr/local/bin/git version
+d0 | main                     | cmd_name     |     |           |           |              | version (version)
+d0 | main                     | def_param    |     |           |           | scope:system | color.ui:never
+d0 | main                     | def_param    |     |           |           | scope:global | color.ui:always
+d0 | main                     | def_param    |     |           |           | scope:local  | color.ui:auto
+d0 | main                     | data         | r0  |  0.002100 |  0.002100 | fsync        | fsync/writeout-only:0
+d0 | main                     | data         | r0  |  0.002126 |  0.002126 | fsync        | fsync/hardware-flush:0
+d0 | main                     | exit         |     |  0.000470 |           |              | code:0
+d0 | main                     | atexit       |     |  0.000477 |           |              | code:0
+----------------
 == Future Work
 
 === Relationship to the Existing Trace Api (api-trace.txt)
diff --git a/Documentation/technical/bitmap-format.txt b/Documentation/technical/bitmap-format.txt
index a85f58f515..c2e652b71a 100644
--- a/Documentation/technical/bitmap-format.txt
+++ b/Documentation/technical/bitmap-format.txt
@@ -72,6 +72,17 @@ MIDXs, both the bit-cache and rev-cache extensions are required.
 	    pack/MIDX. The format and meaning of the name-hash is
 	    described below.
 
+		** {empty}
+		BITMAP_OPT_LOOKUP_TABLE (0x10): :::
+		If present, the end of the bitmap file contains a table
+		containing a list of `N` <commit_pos, offset, xor_row>
+		triplets. The format and meaning of the table is described
+		below.
++
+NOTE: Unlike the xor_offset used to compress an individual bitmap,
+`xor_row` stores an *absolute* index into the lookup table, not a location
+relative to the current entry.
+
 	4-byte entry count (network byte order): ::
 	    The total count of entries (bitmapped commits) in this bitmap index.
 
@@ -216,3 +227,31 @@ Note that this hashing scheme is tied to the BITMAP_OPT_HASH_CACHE flag.
 If implementations want to choose a different hashing scheme, they are
 free to do so, but MUST allocate a new header flag (because comparing
 hashes made under two different schemes would be pointless).
+
+Commit lookup table
+-------------------
+
+If the BITMAP_OPT_LOOKUP_TABLE flag is set, the last `N * (4 + 8 + 4)`
+bytes (preceding the name-hash cache and trailing hash) of the `.bitmap`
+file contains a lookup table specifying the information needed to get
+the desired bitmap from the entries without parsing previous unnecessary
+bitmaps.
+
+For a `.bitmap` containing `nr_entries` reachability bitmaps, the table
+contains a list of `nr_entries` <commit_pos, offset, xor_row> triplets
+(sorted in the ascending order of `commit_pos`). The content of i'th
+triplet is -
+
+	* {empty}
+	commit_pos (4 byte integer, network byte order): ::
+	It stores the object position of a commit (in the midx or pack
+	index).
+
+	* {empty}
+	offset (8 byte integer, network byte order): ::
+	The offset from which that commit's bitmap can be read.
+
+	* {empty}
+	xor_row (4 byte integer, network byte order): ::
+	The position of the triplet whose bitmap is used to compress
+	this one, or `0xffffffff` if no such bitmap exists.
diff --git a/Documentation/technical/scalar.txt b/Documentation/technical/scalar.txt
index f6353375f0..0600150b3a 100644
--- a/Documentation/technical/scalar.txt
+++ b/Documentation/technical/scalar.txt
@@ -87,17 +87,20 @@ series have been accepted:
 - `scalar-generalize-diagnose`: Move the functionality of `scalar diagnose`
   into `git diagnose` and `git bugreport --diagnose`.
 
+- 'scalar-add-fsmonitor: Enable the built-in FSMonitor in Scalar
+  enlistments. At the end of this series, Scalar should be feature-complete
+  from the perspective of a user.
+
 Roughly speaking (and subject to change), the following series are needed to
 "finish" this initial version of Scalar:
 
-- Finish Scalar features: Enable the built-in FSMonitor in Scalar enlistments
-  and implement `scalar help`. At the end of this series, Scalar should be
-  feature-complete from the perspective of a user.
-
 - Move Scalar to toplevel: Move Scalar out of `contrib/` and into the root of
-  `git`, including updates to build and install it with the rest of Git. This
-  change will incorporate Scalar into the Git CI and test framework, as well as
-  expand regression and performance testing to ensure the tool is stable.
+  `git`. This includes a variety of related updates, including:
+    - building & installing Scalar in the Git root-level 'make [install]'.
+    - builing & testing Scalar as part of CI.
+    - moving and expanding test coverage of Scalar (including perf tests).
+    - implementing 'scalar help'/'git help scalar' to display scalar
+      documentation.
 
 Finally, there are two additional patch series that exist in Microsoft's fork of
 Git, but there is no current plan to upstream them. There are some interesting