Use trace_performance to measure and print execution time and command line
arguments of the entire main() function. In constrast to the shell's 'time'
utility, which measures total time of the parent process, this logs all
involved git commands recursively. This is particularly useful to debug
performance issues of scripted commands (i.e. which git commands were
called with which parameters, and how long did they execute).

Due to git's deliberate use of exit(), the implementation uses an atexit
routine rather than just adding trace_performance_since() at the end of
main().

Usage example: > GIT_TRACE_PERFORMANCE=~/git-trace.log git stash list

Creates a log file like this:
23:57:38.638765 trace.c:405 performance: 0.000310107 s: git command: 'git' 'rev-parse' '--git-dir'
23:57:38.644387 trace.c:405 performance: 0.000261759 s: git command: 'git' 'rev-parse' '--show-toplevel'
23:57:38.646207 trace.c:405 performance: 0.000304468 s: git command: 'git' 'config' '--get-colorbool' 'color.interactive'
23:57:38.648491 trace.c:405 performance: 0.000241667 s: git command: 'git' 'config' '--get-color' 'color.interactive.help' 'red bold'
23:57:38.650465 trace.c:405 performance: 0.000243063 s: git command: 'git' 'config' '--get-color' '' 'reset'
23:57:38.654850 trace.c:405 performance: 0.025126313 s: git command: 'git' 'stash' 'list'
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Add trace_performance and trace_performance_since macros that print a
duration and an optional printf-formatted text to the file specified in
environment variable GIT_TRACE_PERFORMANCE.

These macros, in conjunction with getnanotime(), are intended to simplify
performance measurements from within the application (i.e. profiling via
manual instrumentation, rather than using an external profiling tool).

Unless enabled via GIT_TRACE_PERFORMANCE, these macros have no noticeable
impact on performance, so that test code for well known time killers may
be shipped in release builds. Alternatively, a developer could provide an
additional performance patch (not meant for master) that allows reviewers
to reproduce performance tests more easily, e.g. on other platforms or
using their own repositories.

Usage examples:

Simple use case (measure one code section):

  uint64_t start = getnanotime();
  /* code section to measure */
  trace_performance_since(start, "foobar");

Complex use case (measure repetitive code sections):

  uint64_t t = 0;
  for (;;) {
    /* ignore */
    t -= getnanotime();
    /* code section to measure */
    t += getnanotime();
    /* ignore */
  }
  trace_performance(t, "frotz");
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Add a getnanotime() function that returns nanoseconds since 01/01/1970 as
unsigned 64-bit integer (i.e. overflows in july 2554). This is easier to
work with than e.g. struct timeval or struct timespec. Basing the timer on
the epoch allows using the results with other time-related APIs.

To simplify adaption to different platforms, split the implementation into
a common getnanotime() and a platform-specific highres_nanos() function.

The common getnanotime() function handles errors, falling back to
gettimeofday() if highres_nanos() isn't implemented or doesn't work.

getnanotime() is also responsible for normalizing to the epoch. The offset
to the system clock is calculated only once on initialization, i.e.
manually setting the system clock has no impact on the timer (except if
the fallback gettimeofday() is in use). Git processes are typically short
lived, so we don't need to handle clock drift.

The highres_nanos() function returns monotonically increasing nanoseconds
relative to some arbitrary point in time (e.g. system boot), or 0 on
failure. Providing platform-specific implementations should be relatively
easy, e.g. adapting to clock_gettime() as defined by the POSIX realtime
extensions is seven lines of code.

This version includes highres_nanos() implementations for:
 * Linux: using clock_gettime(CLOCK_MONOTONIC)
 * Windows: using QueryPerformanceCounter()

Todo:
 * enable clock_gettime() on more platforms
 * add Mac OSX version, e.g. using mach_absolute_time + mach_timebase_info
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

This is useful to see where trace output came from.

Add 'const char *file, int line' parameters to the printing functions and
rename them to *_fl.

Add trace_printf* and trace_strbuf macros resolving to the *_fl functions
and let the preprocessor fill in __FILE__ and __LINE__.

As the trace_printf* functions take a variable number of arguments, this
requires variadic macros (i.e. '#define foo(...) foo_impl(__VA_ARGS__)'.
Though part of C99, it is unclear whether older compilers support this.
Thus keep the old functions and only enable variadic macros for GNUC and
MSVC 2005+ (_MSC_VER 1400). This has the nice side effect that the old
C-style declarations serve as documentation how the macros are to be used.

Print 'file:line ' as prefix to each trace line. Align the remaining trace
output at column 40 to accommodate 18 char file names + 4 digit line
number (currently there are 30 *.c files of length 18 and just 11 of 19).
Trace output from longer source files (e.g. builtin/receive-pack.c) will
not be aligned.
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

No functional changes, just move stuff around so that the next patch isn't
that ugly...
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

This is useful to tell apart trace output of separate test runs.

It can also be used for basic, coarse-grained performance analysis. Note
that the accuracy is tainted by writing to the trace file, and you have to
calculate the deltas yourself (which is next to impossible if multiple
threads or processes are involved).
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Some unit-tests use trace output to verify internal state, and unstable
output such as timestamps and line numbers are not useful there.

Disable additional trace output if GIT_TRACE_BARE is set.
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

To be able to add a common prefix or suffix to all trace output (e.g.
a timestamp or file:line of the caller), factor out common setup and
cleanup tasks of the trace* functions.

When adding a common prefix, it makes sense that the output of each trace
call starts on a new line. Add '\n' in case the caller forgot.

Note that this explicitly limits trace output to line-by-line, it is no
longer possible to trace-print just part of a line. Until now, this was
just an implicit assumption (trace-printing part of a line worked, but
messed up the trace file if multiple threads or processes were involved).

Thread-safety / inter-process-safety is also the reason why we need to do
the prefixing and suffixing in memory rather than issuing multiple write()
calls. Write_or_whine_pipe() / xwrite() is atomic unless the size exceeds
MAX_IO_SIZE (8MB, see wrapper.c). In case of trace_strbuf, this costs an
additional string copy (which should be irrelevant for performance in light
of actual file IO).

While we're at it, rename trace_strbuf's 'buf' argument, which suggests
that the function is modifying the buffer. Trace_strbuf() currently is the
only trace API that can print arbitrary binary data (without barfing on
'%' or stopping at '\0'), so 'data' seems more appropriate.
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

This changes GIT_TRACE_PACK_ACCESS functionality as follows:
 * supports the same options as GIT_TRACE (e.g. printing to stderr)
 * no longer supports relative paths
 * appends to the trace file rather than overwriting
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Separate GIT_TRACE description into what it prints and how to configure
where trace output is printed to. Change other GIT_TRACE_* descriptions to
refer to GIT_TRACE.

Add descriptions for GIT_TRACE_SETUP and GIT_TRACE_SHALLOW.
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The trace API currently rechecks the environment variable and reopens the
trace file on every API call. This has the ugly side effect that errors
(e.g. file cannot be opened, or the user specified a relative path) are
also reported on every call. Performance can be improved by about factor
three by remembering the environment state and keeping the file open.

Replace the 'const char *key' parameter in the API with a pointer to a
'struct trace_key' that bundles the environment variable name with
additional, trace-internal state. Change the call sites of these APIs to
use a static 'struct trace_key' instead of a string constant.

In trace.c::get_trace_fd(), save and reuse the file descriptor in 'struct
trace_key'.

Add a 'trace_disable()' API, so that packet_trace() can cleanly disable
tracing when it encounters packed data (instead of using unsetenv()).
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

trace_printf_key() is the only non-static function that duplicates the
printf format attribute in the .c file, remove it for consistency.
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The format parameter to trace_printf functions is sometimes abbreviated
'fmt'. Rename to 'format' everywhere (consistent with POSIX' printf
specification).
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Also include direct dependencies (strbuf.h and git-compat-util.h for
__attribute__) so that trace.h can be used independently of cache.h, e.g.
in test programs.
Signed-off-by: NKarsten Blees <blees@dcon.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Allow specifying only certain individual test pieces to be run
using a range notation (e.g. "t1234-test.sh --run='1-4 6 8 9-'").

* ib/test-selectively-run:
  t0000-*.sh: fix the GIT_SKIP_TESTS sub-tests
  test-lib: '--run' to run only specific tests
  test-lib: tests skipped by GIT_SKIP_TESTS say so
  test-lib: document short options in t/README

* ta/string-list-init:
  string-list: spell all values out that are given to a string_list initializer

* jm/dedup-test-config:
  t/t7810-grep.sh: remove duplicate test_config()

* dt/refs-check-refname-component-optim:
  refs.c: optimize check_refname_component()

* sk/test-cmp-bin:
  t5000, t5003: do not use test_cmp to compare binary files

* sh/enable-preloadindex:
  environment.c: enable core.preloadindex by default

* rs/read-ref-at:
  refs.c: change read_ref_at to use the reflog iterators

* jk/error-resolve-conflict-advice:
  error_resolve_conflict: drop quotations around operation
  error_resolve_conflict: rewrap advice message

Avoid unnecessary copy of previous contents when extending the
hashtable used in pack-objects.

* rs/pack-objects-no-unnecessary-realloc:
  pack-objects: use free()+xcalloc() instead of xrealloc()+memset()

* lt/log-auto-decorate:
  git log: support "auto" decorations

* jm/doc-wording-tweaks:
  Documentation: wording fixes in the user manual and glossary

* jm/format-patch-mail-sig:
  format-patch: add "--signature-file=<file>" option
  format-patch: make newline after signature conditional

Propagate the error messages from the webserver better to the
client coming over the HTTP transport.

* jk/http-errors:
  http: default text charset to iso-8859-1
  remote-curl: reencode http error messages
  strbuf: add strbuf_reencode helper
  http: optionally extract charset parameter from content-type
  http: extract type/subtype portion of content-type
  t5550: test display of remote http error messages
  t/lib-httpd: use write_script to copy CGI scripts
  test-lib: preserve GIT_CURL_VERBOSE from the environment

mailmap.file configuration names a pathname, hence should honor
~/path and ~user/path as its value.

* ow/config-mailmap-pathname:
  config: respect '~' and '~user' in mailmap.file

Allow remote-helper/fast-import based transport to rename the refs
while transferring the history.

* fc/remote-helper-refmap:
  transport-helper: remove unnecessary strbuf resets
  transport-helper: add support to delete branches
  fast-export: add support to delete refs
  fast-import: add support to delete refs
  transport-helper: add support to push symbolic refs
  transport-helper: add support for old:new refspec
  fast-export: add new --refspec option
  fast-export: improve argument parsing

"git gc --auto" was recently changed to run in the background to
give control back early to the end-user sitting in front of the
terminal, but it forgot that housekeeping involving reflogs should
be done without other processes competing for accesses to the refs.

* nd/daemonize-gc:
  gc --auto: do not lock refs in the background

* jm/t9138-style-fix:
  t9138-git-svn-authors-prog.sh fixups

* jm/instaweb-apache-24:
  git-instaweb: add support for Apache 2.4

"git remote rm" and "git remote prune" can involve removing many
refs at once, which is not a very efficient thing to do when very
many refs exist in the packed-refs file.

* jl/remote-rm-prune:
  remote prune: optimize "dangling symref" check/warning
  remote: repack packed-refs once when deleting multiple refs
  remote rm: delete remote configuration as the last

The completion code did not know about quite a few options that are
common between "git merge" and "git pull", and a couple of options
unique to "git merge".

* jk/complete-merge-pull:
  completion: add missing options for git-merge
  completion: add a note that merge options are shared

Like calloc(3), xcalloc() takes nmemb and then size.

* bg/xcalloc-nmemb-then-size:
  transport-helper.c: rearrange xcalloc arguments
  remote.c: rearrange xcalloc arguments
  reflog-walk.c: rearrange xcalloc arguments
  pack-revindex.c: rearrange xcalloc arguments
  notes.c: rearrange xcalloc arguments
  imap-send.c: rearrange xcalloc arguments
  http-push.c: rearrange xcalloc arguments
  diff.c: rearrange xcalloc arguments
  config.c: rearrange xcalloc arguments
  commit.c: rearrange xcalloc arguments
  builtin/remote.c: rearrange xcalloc arguments
  builtin/ls-remote.c: rearrange xcalloc arguments

submodule.*.ignore and diff.ignoresubmodules are used to ignore all
submodule changes in "diff" output, but it can be confusing to
apply these configuration values to status and commit.

This is a backward-incompatible change, but should be so in a good
way (aka bugfix).

* jl/status-added-submodule-is-never-ignored:
  commit -m: commit staged submodules regardless of ignore config
  status/commit: show staged submodules regardless of ignore config

Compatibility enhancement for Solaris.

* cb/byte-order:
  compat/bswap.h: fix endianness detection
  compat/bswap.h: restore preference __BIG_ENDIAN over BIG_ENDIAN
  compat/bswap.h: detect endianness on more platforms that don't use BYTE_ORDER

* jk/strbuf-tolower:
  strbuf: add strbuf_tolower function

* jk/daemon-tolower:
  daemon/config: factor out duplicate xstrdup_tolower