[PATCH v7 00/16] add performance tracing facility

...slowly turning into a full-fledged trace overhaul...

When working on the documentation, I discovered GIT_TRACE_PACK_ACCESS, which uses a completely separate trace implementation that is 3 times faster by keeping the file open...so this round includes a performance patch that brings the trace API up to speed.

Changes since v6:
[04-06]: New.
[07-08]: Separated the 'disable for test' aspect into a separate patch.
         GIT_TRACE_BARE=1 is set in test-lib.sh rather than individual
         tests. Moved static trace_bare variable from global scope into
         prepare_trace_line().
[09]:    Cast timeval.tv_usec to long to prevent compiler warning.
[11,13]: Factor out '#define TRACE_CONTEXT __FILE__' so that it can
         be easily changed to __FUNCTION__.
[14]:    Added GIT_TRACE_PERFORMANCE to Documentation/git.txt
[15-16]: New.

[01-03,10,12] are unchanged save resolving conflicts.

Karsten Blees (16):
  trace: move trace declarations from cache.h to new trace.h
  trace: consistently name the format parameter
  trace: remove redundant printf format attribute
  trace: improve trace performance
  Documentation/git.txt: improve documentation of 'GIT_TRACE*' variables
  sha1_file: change GIT_TRACE_PACK_ACCESS logging to use trace API
  trace: add infrastructure to augment trace output with additional info
  trace: disable additional trace output for unit tests
  trace: add current timestamp to all trace output
  trace: move code around, in preparation to file:line output
  trace: add 'file:line' to all trace output
  trace: add high resolution timer function to debug performance issues
  trace: add trace_performance facility to debug performance issues
  git: add performance tracing for git's main() function to debug
    scripts
  wt-status: simplify performance measurement by using getnanotime()
  progress: simplify performance measurement by using getnanotime()

 Documentation/git.txt  |  59 +++++---
 Makefile               |   7 +
 builtin/receive-pack.c |   2 +-
 cache.h                |  13 +-
 commit.h               |   1 +
 config.mak.uname       |   1 +
 git-compat-util.h      |   4 +
 git.c                  |   2 +
 pkt-line.c             |   8 +-
 progress.c             |  71 +++++-----
 sha1_file.c            |  30 +---
 shallow.c              |  10 +-
 t/test-lib.sh          |   4 +
 trace.c                | 369 ++++++++++++++++++++++++++++++++++++++++---------
 trace.h                | 105 ++++++++++++++
 wt-status.c            |  14 +-
 16 files changed, 524 insertions(+), 176 deletions(-)
 create mode 100644 trace.h