test-generation: compute generation numbers and clock skews

It finds three commits that has older commit timestamp than the
newest commit timestamp among its ancestor in our history; all of
these are a direct child of a commit that is older (i.e. the clock
skew lasts for only one hop).

  commit  gen  timestamp                 skew gen ancestor
  ed19f36 2870 2006-03-04 07:29:56 +0000 (8) 2869 91a6bf4
  7763987 6404 2007-09-02 06:53:47 +0000 (373) 6403 86bab96
  619a644 9982 2009-10-18 19:34:56 +0000 (268948) 9981 46148dd

On the other hand, the kernel history is littered with skewed
chains.  I counted 2239 commits that have an ancestor newer than
themselves in total (they tend to cluster, but I haven't counted
clusters), among 322345 commits (0.7%).

For example, a 33-commit chain leading to b4e1b7e builds on top of
422e6c4 that was commited by Linus at Tue Mar 15 15:48:13 2011, but
the tip commit claims to have been committed at Sun Feb 20 19:19:43
2011, which is clearly impossible.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
clone --single: limit the fetch refspec to fetched branch

After running "git clone --single", the resulting repository has the
usual default "+refs/heads/*:refs/remotes/origin/*" wildcard fetch
refspec installed, which means that a subsequent "git fetch" will
end up grabbing all the other branches.

Update the fetch refspec to cover only the singly cloned ref instead
to correct this.

Signed-off-by: Ralf Thielow <ralf.thielow@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add MALLOC_CHECK_ and MALLOC_PERTURB_ libc env to the test suite for detecting heap corruption

Recent versions of Linux libc (later than 5.4.23) and glibc (2.x)
include a malloc() implementation which is tunable via environment
variables. When MALLOC_CHECK_ is set, a special (less efficient)
implementation is used which is designed to be tolerant against
simple errors, such as double calls of free() with the same argument,
or overruns of a single byte (off-by-one bugs). When MALLOC_CHECK_
is set to 3, a diagnostic message is printed on stderr
and the program is aborted.

Setting the MALLOC_PERTURB_ environment variable causes the malloc
functions in libc to return memory which has been wiped and clear
memory when it is returned.
Of course this does not affect calloc which always does clear the memory.

The reason for this exercise is, of course, to find code which uses
memory returned by malloc without initializing it and code which uses
code after it is freed. valgrind can do this but it's costly to run.
The MALLOC_PERTURB_ exchanges the ability to detect problems in 100%
of the cases with speed.

The byte value used to initialize values returned by malloc is the byte
value of the environment value. The value used to clear memory is the
bitwise inverse. Setting MALLOC_PERTURB_ to zero disables the feature.

This technique can find hard to detect bugs.
It is therefore suggested to always use this flag (at least temporarily)
when testing out code or a new distribution.

But the test suite can use also valgrind(memcheck) via 'make valgrind'
or 'make GIT_TEST_OPTS="--valgrind"'.

Memcheck wraps client calls to malloc(), and puts a "red zone" on
each end of each block in order to detect access overruns.
Memcheck already detects double free() (up to the limit of the buffer
which remembers pending free()). Thus memcheck subsumes all the
documented coverage of MALLOC_CHECK_.

If MALLOC_CHECK_ is set non-zero when running memcheck, then the
overruns that might be detected by MALLOC_CHECK_ would be overruns
on the wrapped blocks which include the red zones.  Thus MALLOC_CHECK_
would be checking memcheck, and not the client.  This is not useful,
and actually is wasteful.  The only possible [documented] advantage
of using MALLOC_CHECK_ and memcheck together, would be if MALLOC_CHECK_
detected duplicate free() in more cases than memcheck because memcheck's
buffer is too small.

Therefore we don't use MALLOC_CHECK_ and valgrind(memcheck) at the
same time.

Signed-off-by: Elia Pinto <gitter.spiros@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
MALLOC_CHECK: various clean-ups

The most important in this change is to avoid affecting anything
when test-lib is used from perf-lib.  It also limits the effect of
the MALLOC_CHECK only to what is run inside the actual test.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'rs/archive-zip-utf8' into jch

Need help from people on platforms on which Zip matters to see
compatiblity with other people's zip implementations.

Will merge to 'master' as part of the sixth batch.

* rs/archive-zip-utf8:
  archive-zip: support UTF-8 paths
Merge branch 'jc/maint-blame-no-such-path' into jch

"git blame MAKEFILE" run in a history that has "Makefile" but not
"MAKEFILE" should say "No such file MAKEFILE in HEAD", but got
confused on a case insensitive filesystem and failed to do so.

Even during a conflicted merge, "git blame $path" always meant to
blame uncommitted changes to the "working tree" version; make it
more useful by showing cleanly merged parts as coming from the other
branch that is being merged.

Will merge to 'master' as part of the seventh batch.

* jc/maint-blame-no-such-path:
  blame: allow "blame file" in the middle of a conflicted merge
  blame $path: avoid getting fooled by case insensitive filesystems
Merge branch 'mh/string-list' into jch

Will merge to 'master' as part of the seventh batch.

* mh/string-list:
  api-string-list.txt: initialize the string_list the easy way
  string_list: add a function string_list_longest_prefix()
  string_list: add a new function, string_list_remove_duplicates()
  string_list: add a new function, filter_string_list()
  string_list: add two new functions for splitting strings
  string_list: add function string_list_append_nodup()
Merge branch 'mh/fetch-filter-refs' into jch

Code simplification and clarification.

Will merge to 'master' as part of the seventh batch.

* mh/fetch-filter-refs:
  fetch-pack: eliminate spurious error messages
  cmd_fetch_pack(): simplify computation of return value
  fetch-pack: report missing refs even if no existing refs were received
  cmd_fetch_pack(): return early if finish_connect() fails
  filter_refs(): simplify logic
  filter_refs(): build refs list as we go
  filter_refs(): delete matched refs from sought list
  fetch_pack(): update sought->nr to reflect number of unique entries
  filter_refs(): do not check the same sought_pos twice
  Change fetch_pack() and friends to take string_list arguments
  fetch_pack(): reindent function decl and defn
  Rename static function fetch_pack() to http_fetch_pack()
  t5500: add tests of fetch-pack --all --depth=N $URL $REF
  t5500: add tests of error output for missing refs
Merge branch 'jk/config-warn-on-inaccessible-paths' into jch

The attribute system may be asked for a path whose leading
directories do not exist in the current working tree.  In addition
to ENOENT, ENOTDIR must be ignored.

Will merge to 'master' as part of the seventh batch.

* jk/config-warn-on-inaccessible-paths:
  attr: failure to open a .gitattributes file is OK with ENOTDIR
Merge branch 'nd/maint-diffstat-summary' into jch

Earlier we made the diffstat summary line that shows the number of
lines added/deleted localizable, but it was found irritating having
to see them in various languages on a list whose discussion language
is English.

The original had trivial thinko in reverting Q_(), which has been
fixed.

Will merge to 'master' as part of the seventh batch.

* nd/maint-diffstat-summary:
  Revert diffstat back to English
Merge branch 'jc/maint-log-grep-all-match' (early part) into jch

* 'jc/maint-log-grep-all-match' (early part):
  log: document use of multiple commit limiting options
  log --grep/--author: honor --all-match honored for multiple --grep patterns
  grep: show --debug output only once
  grep: teach --debug option to dump the parse tree

Conflicts:
	builtin/grep.c
Merge branch 'jw/doc-commit-title' into jch

Update parts of document that talked about "first line of commit
log" to say "title of commit" with definition of what that "title"
is.

Will merge to 'master' as part of the seventh batch.

* jw/doc-commit-title:
  Documentation: describe subject more precisely
Merge branch 'nd/fetch-status-alignment' into jch

Will merge to 'next'.

* nd/fetch-status-alignment:
  fetch: align per-ref summary report in UTF-8 locales
Merge branch 'mv/cherry-pick-s' into jch

Will merge to 'next'.

* mv/cherry-pick-s:
  cherry-pick: don't forget -s on failure
Merge branch 'jk/no-more-pre-exec-callback' into pu

(Originally merged to 'next' on 2012-07-23)

Will defer until the end of the 2012.
while waiting for older "less" to go extinct.

* jk/no-more-pre-exec-callback:
  pager: drop "wait for output to run less" hack
Merge branch 'pw/p4-submit-conflicts' into pu

Waiting for comments.

* pw/p4-submit-conflicts:
  git-p4: add submit --conflict option and config varaiable
  git p4: add submit --prepare-p4-only option
  git p4: add submit --dry-run option
  git p4: accept -v for --verbose
  git p4: revert deleted files after submit cancel
  git p4: rearrange submit template construction
  git p4: test clean-up after failed submit, fix added files
  git p4: standardize submit cancel due to unchanged template
  git p4: move conflict prompt into run, add [q]uit input
  git p4: remove submit failure options [a]pply and [w]rite
  git p4: gracefully fail if some commits could not be applied
  git p4 test: remove bash-ism of combined export/assignment
Merge branch 'fa/remote-svn' into pu

A GSoC project.  Looked promising.
Waiting for comments from mentors and stakeholders.

* fa/remote-svn:
  Add a test script for remote-svn
  remote-svn: add marks-file regeneration
  Add a svnrdump-simulator replaying a dump file for testing
  remote-svn: add incremental import
  remote-svn: Activate import/export-marks for fast-import
  Create a note for every imported commit containing svn metadata
  vcs-svn: add fast_export_note to create notes
  Allow reading svn dumps from files via file:// urls
  remote-svn, vcs-svn: Enable fetching to private refs
  When debug==1, start fast-import with "--stats" instead of "--quiet"
  Add documentation for the 'bidi-import' capability of remote-helpers
  Connect fast-import to the remote-helper via pipe, adding 'bidi-import' capability
  Add argv_array_detach and argv_array_free_detached
  Add svndump_init_fd to allow reading dumps from arbitrary FDs
  Add git-remote-testsvn to Makefile and .gitignore
  Implement a remote helper for svn in C
Merge branch 'fa/vcs-svn' into pu

A GSoC project.  Looked promising.
Waiting for comments from mentors and stakeholders.

* fa/vcs-svn:
  vcs-svn: remove repo_tree
  vcs-svn/svndump: rewrite handle_node(), begin|end_revision()
  vcs-svn/svndump: restructure node_ctx, rev_ctx handling
  svndump: move struct definitions to .h
Merge branch 'er/doc-fast-import-done' into pu

Parked in 'pu' in case ESR responds with "Sorry, forgot to sign-off".

* er/doc-fast-import-done:
  fast-import: document the --done option
Merge branch 'jc/add-delete-default' into pu

"git add dir/" updated modified files and added new files, but does
not notice removed files, which may be "Huh?" to some users.  They
can of course use "git add -A dir/", but why should they?

Resurrected from graveyard, as I thought it was a worthwhile thing
to do in the longer term.

Waiting for comments.

* jc/add-delete-default:
  git add: notice removal of tracked paths by default