This function was added in d2b0708e (2008-09-27, add have_git_dir()
function) as a preparation for adbc0b6b (2008-09-30, cygwin: Use native
Win32 API for stat).

However the second referenced commit was reverted in f66450ae (2013-06-22,
cygwin: Remove the Win32 l/stat() implementation), so we don't need to
expose this wrapper function any more as a public API.
Signed-off-by: NStefan Beller <stefanbeller@googlemail.com>
Acked-by: NMichael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The said function has this signature:

	extern int checkout_entry(struct cache_entry *ce,
				  const struct checkout *state,
				  char *topath);

At first glance, it might appear that the caller of checkout_entry()
can specify to which path the contents are written out by the last
parameter, and it is tempting to add "const" in front of its type.

In reality, however, topath[] is to point at a buffer to store the
temporary path generated by the callchain originating from this
function, and the temporary path is always short, much shorter than
the buffer prepared by its only caller in builtin/checkout-index.c.

Document the code a bit to clarify so that future callers know how
to use the function better.
Noticed-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Using a relative_path as git_dir first appears in v1.5.6-1-g044bbbcb.
It will make git_dir shorter only if git_dir is inside work_tree,
and this will increase performance. But my last refactor effort on
relative_path function (commit v1.8.3-rc2-12-ge02ca72f) changed that.
Always use relative_path as git_dir may bring troubles like
$gmane/234434.

Because new relative_path is a combination of original relative_path
from path.c and original path_relative from quote.c, so in order to
restore the origin implementation, save the original relative_path
as remove_leading_path, and call it in setup.c.
Suggested-by: NKarsten Blees <karsten.blees@gmail.com>
Signed-off-by: NJiang Xin <worldhello.net@gmail.com>
Signed-off-by: NJonathan Nieder <jrnieder@gmail.com>

Commit a9080475 taught format-patch the "--from" option,
which places the author ident into an in-body from header,
and uses the committer ident in the rfc822 from header.  The
documentation claims that it will omit the in-body header
when it is the same as the rfc822 header, but the code never
implemented that behavior.

This patch completes the feature by comparing the two idents
and doing nothing when they are the same (this is the same
as simply omitting the in-body header, as the two are by
definition indistinguishable in this case). This makes it
reasonable to turn on "--from" all the time (if it matches
your particular workflow), rather than only using it when
exporting other people's patches.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

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

Depending upon the absence or presence of a trailing '/' on the incoming
pathname, index_name_exists() checks either if a file is present in the
index or if a directory is represented within the index. Each caller
explicitly chooses the mode of operation by adding or removing a
trailing '/' before invoking index_name_exists().

Since these two modes of operations are disjoint and have no code in
common (one searches index_state.name_hash; the other dir_hash), they
can be represented more naturally as distinct functions: one to search
for a file, and one for a directory.

Splitting index searching into two functions relieves callers of the
artificial burden of having to add or remove a slash to select the mode
of operation; instead they just call the desired function. A subsequent
patch will take advantage of this benefit in order to eliminate the
requirement that the incoming pathname for a directory search must have
a trailing slash.

(In order to avoid disturbing in-flight topics, index_name_exists() is
retained as a thin wrapper dispatching either to index_dir_exists() or
index_file_exists().)
Signed-off-by: NEric Sunshine <sunshine@sunshineco.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

When you run "git config --int", the maximum size of integer
you get depends on how git was compiled, and what it
considers to be an "int".

This is almost useful, because your scripts calling "git
config" will behave similarly to git internally. But relying
on this is dubious; you have to actually know how git treats
each value internally (e.g., int versus unsigned long),
which is not documented and is subject to change. And even
if you know it is "unsigned long", we do not have a
git-config option to match that behavior.

Furthermore, you may simply be asking git to store a value
on your behalf (e.g., configuration for a hook). In that
case, the relevant range check has nothing at all to do with
git, but rather with whatever scripting tools you are using
(and git has no way of knowing what the appropriate range is
there).

Not only is the range check useless, but it is actively
harmful, as there is no way at all for scripts to look
at config variables with large values. For instance, one
cannot reliably get the value of pack.packSizeLimit via
git-config. On an LP64 system, git happily uses a 64-bit
"unsigned long" internally to represent the value, but the
script cannot read any value over 2G.

Ideally, the "--int" option would simply represent an
arbitrarily large integer. For practical purposes, however,
a 64-bit integer is large enough, and is much easier to
implement (and if somebody overflows it, we will still
notice the problem, and not simply return garbage).
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

This is useful to make sure we don't step outside the boundaries of what
we are interpreting at the moment. For example while interpreting
foobar@{u}~1, the job of interpret_branch_name() ends right before ~1,
but there's no way to figure that out inside the function, unless the
len argument is passed.

So let's do that.
Signed-off-by: NFelipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Use the fixed width integer types uint16_t and uint32_t for on-disk
structures; unsigned short and unsigned int do not have a guaranteed
size.
Signed-off-by: NThomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NOndřej Bílka <neleai@seznam.cz>
Reviewed-by: NMarc Branchaud <marcnarc@xiplink.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Both daemon.c and shell.c contain logic to open FDs 0/1/2 from
/dev/null if they are not already open.  Move the function in daemon.c
to setup.c and use it in shell.c, too.

While there, remove a 'not' that inverted the meaning of the comment.
The point is indeed to *avoid* messing up.
Signed-off-by: NThomas Rast <trast@inf.ethz.ch>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

:(glob)path differs from plain pathspec that it uses wildmatch with
WM_PATHNAME while the other uses fnmatch without FNM_PATHNAME. The
difference lies in how '*' (and '**') is processed.

With the introduction of :(glob) and :(literal) and their global
options --[no]glob-pathspecs, the user can:

 - make everything literal by default via --noglob-pathspecs
   --literal-pathspecs cannot be used for this purpose as it
   disables _all_ pathspec magic.

 - individually turn on globbing with :(glob)

 - make everything globbing by default via --glob-pathspecs

 - individually turn off globbing with :(literal)

The implication behind this is, there is no way to gain the default
matching behavior (i.e. fnmatch without FNM_PATHNAME). You either get
new globbing or literal. The old fnmatch behavior is considered
deprecated and discouraged to use.
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Prepending prefix to pathspec is a trick to workaround the fact that
commands can be executed in a subdirectory, but all git commands run
at worktree's root. The prefix part should always be treated as
literal string. Make it so.
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Each caller of sha1_object_info_extended sets up an
object_info struct to tell the function which elements of
the object it wants to get. Until now, getting the type of
the object has always been required (and it is returned via
the return type rather than a pointer in object_info).

This can involve actually opening a loose object file to
determine its type, or following delta chains to determine a
packed file's base type. These effects produce a measurable
slow-down when doing a "cat-file --batch-check" that does
not include %(objecttype).

This patch adds a "typep" query to struct object_info, so
that it can be optionally queried just like size and
disk_size. As a result, the return type of the function is
no longer the object type, but rather 0/-1 for success/error.

As there are only three callers total, we just fix up each
caller rather than keep a compatibility wrapper:

  1. The simpler sha1_object_info wrapper continues to
     always ask for and return the type field.

  2. The istream_source function wants to know the type, and
     so always asks for it.

  3. The cat-file batch code asks for the type only when
     %(objecttype) is part of the format string.

On linux.git, the best-of-five for running:

  $ git rev-list --objects --all >objects
  $ time git cat-file --batch-check='%(objectsize:disk)'

on a fully packed repository goes from:

  real    0m8.680s
  user    0m8.160s
  sys     0m0.512s

to:

  real    0m7.205s
  user    0m6.580s
  sys     0m0.608s
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

A common use of "cat-file --batch-check" is to feed a list
of objects from "rev-list --objects" or a similar command.
In this instance, all of our input objects are 40-byte sha1
ids. However, cat-file has always allowed arbitrary revision
specifiers, and feeds the result to get_sha1().

Fortunately, get_sha1() recognizes a 40-byte sha1 before
doing any hard work trying to look up refs, meaning this
scenario should end up spending very little time converting
the input into an object sha1. However, since 798c35fc
(get_sha1: warn about full or short object names that look
like refs, 2013-05-29), when we encounter this case, we
spend the extra effort to do a refname lookup anyway, just
to print a warning. This is further exacerbated by ca919930
(get_packed_ref_cache: reload packed-refs file when it
changes, 2013-06-20), which makes individual ref lookup more
expensive by requiring a stat() of the packed-refs file for
each missing ref.

With no patches, this is the time it takes to run:

  $ git rev-list --objects --all >objects
  $ time git cat-file --batch-check='%(objectname)' <objects

on the linux.git repository:

  real    1m13.494s
  user    0m25.924s
  sys     0m47.532s

If we revert ca919930, the packed-refs up-to-date check, it
gets a little better:

  real    0m54.697s
  user    0m21.692s
  sys     0m32.916s

but we are still spending quite a bit of time on ref lookup
(and we would not want to revert that patch, anyway, which
has correctness issues).  If we revert 798c35fc, disabling
the warning entirely, we get a much more reasonable time:

  real    0m7.452s
  user    0m6.836s
  sys     0m0.608s

This patch does the moral equivalent of this final case (and
gets similar speedups). We introduce a global flag that
callers of get_sha1() can use to avoid paying the price for
the warning.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

This can be used to read configuration values directly from git's
database. For example it is useful for reading to be checked out
.gitmodules files directly from the database.
Signed-off-by: NHeiko Voigt <hvoigt@hvoigt.net>
Acked-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

I attempted to make index_state->cache[] a "const struct cache_entry **"
to find out how existing entries in index are modified and where. The
question I have is what do we do if we really need to keep track of on-disk
changes in the index. The result is

 - diff-lib.c: setting CE_UPTODATE

 - name-hash.c: setting CE_HASHED

 - preload-index.c, read-cache.c, unpack-trees.c and
   builtin/update-index: obvious

 - entry.c: write_entry() may refresh the checked out entry via
   fill_stat_cache_info(). This causes "non-const struct cache_entry
   *" in builtin/apply.c, builtin/checkout-index.c and
   builtin/checkout.c

 - builtin/ls-files.c: --with-tree changes stagemask and may set
   CE_UPDATE

Of these, write_entry() and its call sites are probably most
interesting because it modifies on-disk info. But this is stat info
and can be retrieved via refresh, at least for porcelain
commands. Other just uses ce_flags for local purposes.

So, keeping track of "dirty" entries is just a matter of setting a
flag in index modification functions exposed by read-cache.c. Except
unpack-trees, the rest of the code base does not do anything funny
behind read-cache's back.

The actual patch is less valueable than the summary above. But if
anyone wants to re-identify the above sites. Applying this patch, then
this:

    diff --git a/cache.h b/cache.h
    index 430d021..1692891 100644
    --- a/cache.h
    +++ b/cache.h
    @@ -267,7 +267,7 @@ static inline unsigned int canon_mode(unsigned int mode)
     #define cache_entry_size(len) (offsetof(struct cache_entry,name) + (len) + 1)

     struct index_state {
    -	struct cache_entry **cache;
    +	const struct cache_entry **cache;
     	unsigned int version;
     	unsigned int cache_nr, cache_alloc, cache_changed;
     	struct string_list *resolve_undo;

will help quickly identify them without bogus warnings.
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The definition of "struct ref" in "cache.h", a header file so
central to the system, always confused me.  This structure is not
about the local ref used by sha1-name API to name local objects.

It is what refspecs are expanded into, after finding out what refs
the other side has, to define what refs are updated after object
transfer succeeds to what values.  It belongs to "remote.h" together
with "struct refspec".

While we are at it, also move the types and functions related to the
Git transport connection to a new header file connect.h
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Using sha1_object_info_extended, a caller can find out the
type of an object, its size, and information about where it
is stored. In addition to the object's "true" size, it can
also be useful to know the size that the object takes on
disk (e.g., to generate statistics about which refs consume
space).

This patch adds a "disk_sizep" field to "struct object_info",
and fills it in during sha1_object_info_extended if it is
non-NULL.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Original design of relative_path() is simple, just strip the prefix
(*base) from the absolute path (*abs).

In most cases, we need a real relative path, such as: ../foo,
../../bar.  That's why there is another reimplementation
(path_relative()) in quote.c.

Borrow some codes from path_relative() in quote.c to refactor
relative_path() in path.c, so that it could return real relative
path, and user can reuse this function without reimplementing
his/her own.  The function path_relative() in quote.c will be
substituted, and I would use the new relative_path() function when
implementing the interactive git-clean later.

Different results for relative_path() before and after this refactor:

    abs path  base path  relative (original)  relative (refactor)
    ========  =========  ===================  ===================
    /a/b      /a/b       .                    ./
    /a/b/     /a/b       .                    ./
    /a        /a/b/      /a                   ../
    /         /a/b/      /                    ../../
    /a/c      /a/b/      /a/c                 ../c
    /x/y      /a/b/      /x/y                 ../../x/y

    a/b/      a/b/       .                    ./
    a/b/      a/b        .                    ./
    a         a/b        a                    ../
    x/y       a/b/       x/y                  ../../x/y
    a/c       a/b        a/c                  ../c

    (empty)   (null)     (empty)              ./
    (empty)   (empty)    (empty)              ./
    (empty)   /a/b       (empty)              ./
    (null)    (null)     (null)               ./
    (null)    (empty)    (null)               ./
    (null)    /a/b       (segfault)           ./

You may notice that return value "." has been changed to "./".
It is because:

 * Function quote_path_relative() in quote.c will show the relative
   path as "./" if abs(in) and base(prefix) are the same.

 * Function relative_path() is called only once (in setup.c), and
   it will be OK for the return value as "./" instead of ".".
Signed-off-by: NJiang Xin <worldhello.net@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

It can sometimes be useful to know whether a path in the
filesystem has been updated without going to the work of
opening and re-reading its content. We trust the stat()
information on disk already to handle index updates, and we
can use the same trick here.

This patch introduces a "stat_validity" struct which
encapsulates the concept of checking the stat-freshness of a
file. It is implemented on top of "struct stat_data" to
reuse the logic about which stat entries to trust for a
particular platform, but hides the complexity behind two
simple functions: check and update.
Signed-off-by: NMichael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Add public functions fill_stat_data() and match_stat_data() to work
with it.  This infrastructure will later be used to check the validity
of other types of file.
Signed-off-by: NMichael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

5f44324d (core: log offset pack data accesses happened - 2011-07-06)
provides a way to observe pack access patterns via a config
switch. Setting an environment variable looks more obvious than a
config var, especially when you just need to _observe_, and more
inline with other tracing knobs we have.

Document it as it may be useful for remote troubleshooting.
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

ie_match_stat and ie_modified only derefence their struct cache_entry
pointers for reading.  Add const to the parameter declaration here and
do the same for the static helper function used by them, as it's the
same there as well.  This allows callers to pass in const pointers.
Signed-off-by: NRené Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Add const for pointers that are only dereferenced for reading by the
inline functions copy_cache_entry and ce_mode_from_stat.  This allows
callers to pass in const pointers.
Signed-off-by: NRené Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Each "struct ref" has a boolean flag that is set by the
fetch code to determine whether the ref should be marked as
"not-for-merge" or not when we write it out to FETCH_HEAD.

It would be useful to turn this boolean into a tri-state,
with the third state meaning "do not bother writing it out
to FETCH_HEAD at all". That would let us add extra refs to
the set of refs to be stored (e.g., to store copies of
things we fetched) without impacting FETCH_HEAD.

This patch turns it into an enum that covers the tri-state
case, and hopefully makes the code more explicit and easier
to read.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

"git reflog --expire=all" tries to expire reflog entries up to the
current second, because the approxidate() parser gives the current
timestamp for anything it does not understand (and it does not know
what time "all" means).  When the user tells us to expire "all" (or
set the expiration time to "now"), the user wants to remove all the
reflog entries (no reflog entry should record future time).

Just set it to ULONG_MAX and to let everything that is older that
timestamp expire.

While at it, allow "now" to be treated the same way for callers that
parse expiry date timestamp with this function.  Also use an error
reporting version of approxidate() to report misspelled date.  When
the user says e.g. "--expire=mnoday" to delete entries two days or
older on Wednesday, we wouldn't want the "unknown, default to now"
logic to kick in.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

This allows for optionally getting the size of the returned data and
will be used in a follow-up patch.
Signed-off-by: NLukas Fleischer <git@cryptocrack.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Extract the read_index_data() function from attr.c and move it to
read-cache.c; rename it to read_blob_data_from_index() and update
the function signature of it to align better with index/cache API
functions.

This allows for reusing the function in convert.c later.
Signed-off-by: NLukas Fleischer <git@cryptocrack.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

All calls to set_shared_perm() use mode == 0, so simplify the
function.

Because all callers use the macro adjust_shared_perm(path) from
cache.h to call this function, convert it to a proper function,
losing set_shared_perm().

Since path.c has much more functions than just mkpath() these days,
drop the stale comment about it.
Signed-off-by: NTorsten Bögershausen <tboegi@web.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

A common workflow in large projects is to chdir into a subdirectory of
interest and only do work there:

	cd src
	vi foo.c
	make test
	git add -u
	git commit

The upcoming change to 'git add -u' behavior would not affect such a
workflow: when the only changes present are in the current directory,
'git add -u' will add all changes, and whether that happens via an
implicit "." or implicit ":/" parameter is an unimportant
implementation detail.

The warning about use of 'git add -u' with no pathspec is annoying
because it seemingly serves no purpose in this case.  So suppress the
warning unless there are changes outside the cwd that are not being
added.

A previous version of this patch ran two I/O-intensive diff-files
passes: one to find changes outside the cwd, and another to find
changes to add to the index within the cwd.  This version runs one
full-tree diff and decides for each change whether to add it or warn
and suppress it in update_callback.  As a result, even on very large
repositories "git add -u" will not be significantly slower than the
future default behavior ("git add -u :/"), and the slowdown relative
to "git add -u ." should be a useful clue to users of such
repositories to get into the habit of explicitly passing '.'.
Signed-off-by: NJonathan Nieder <jrnieder@gmail.com>
Acked-by: NJeff King <peff@peff.net>
Improved-by: NJunio C Hamano <gitster@pobox.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

In checkout_paths() we do this

 - for all updated items, call match_pathspec
 - for all items, call match_pathspec (inside unmerge_cache)
 - for all items, call match_pathspec (for showing "path .. is unmerged)
 - for updated items, call match_pathspec and update paths

That's a lot of duplicate match_pathspec(s) and the function is not
exactly cheap to be called so many times, especially on large indexes.
This patch makes it call match_pathspec once per updated index entry,
save the result in ce_flags and reuse the results in the following
loops.

The changes in 0a1283bc (checkout $tree $path: do not clobber local
changes in $path not in $tree - 2011-09-30) limit the affected paths
to ones we read from $tree. We do not do anything to other modified
entries in this case, so the "for all items" above could be modified
to "for all updated items". But..

The command's behavior now is modified slightly: unmerged entries that
match $path, but not updated by $tree, are now NOT touched.  Although
this should be considered a bug fix, not a regression. A new test is
added for this change.

And while at there, free ps_matched after use.

The following command is tested on webkit, 215k entries. The pattern
is chosen mainly to make match_pathspec sweat:

git checkout -- "*[a-zA-Z]*[a-zA-Z]*[a-zA-Z]*"

        before      after
real    0m3.493s    0m2.737s
user    0m2.239s    0m1.586s
sys     0m1.252s    0m1.151s
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

We use the function git_deflate_init() -- which wraps the zlib function
deflateInit() -- to initialize compression of ZIP file entries.  This
results in compressed data prefixed with a two-bytes long header and
followed by a four-bytes trailer.  ZIP file entries consist of ZIP
headers and raw compressed data instead, so we remove the zlib wrapper
before writing the result.

We can ask zlib for the the raw compressed data without the unwanted
parts in the first place by using deflateInit2() and specifying a
negative number of bits to size the window.  For that purpose, factor
out the function do_git_deflate_init() and add git_deflate_init_raw(),
which wraps it.  Then use the latter in archive-zip.c and get rid of
the code that stripped the zlib header and trailer.

Also rename the helper function zlib_deflate() to zlib_deflate_raw()
to reflect the change.

Thus we avoid generating data that we throw away anyway, the code
becomes shorter and some magic constants are removed.
Signed-off-by: NRene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

If an explicit GIT_DIR is given without a working tree, we
implicitly assume that the current working directory should
be used as the working tree. E.g.,:

  GIT_DIR=/some/repo.git git status

would compare against the cwd.

Unfortunately, we fool this rule for sub-invocations of git
by setting GIT_DIR internally ourselves. For example:

  git init foo
  cd foo/.git
  git status ;# fails, as we expect
  git config alias.st status
  git status ;# does not fail, but should

What happens is that we run setup_git_directory when doing
alias lookup (since we need to see the config), set GIT_DIR
as a result, and then leave GIT_WORK_TREE blank (because we
do not have one). Then when we actually run the status
command, we do setup_git_directory again, which sees our
explicit GIT_DIR and uses the cwd as an implicit worktree.

It's tempting to argue that we should be suppressing that
second invocation of setup_git_directory, as it could use
the values we already found in memory. However, the problem
still exists for sub-processes (e.g., if "git status" were
an external command).

You can see another example with the "--bare" option, which
sets GIT_DIR explicitly. For example:

  git init foo
  cd foo/.git
  git status ;# fails
  git --bare status ;# does NOT fail

We need some way of telling sub-processes "even though
GIT_DIR is set, do not use cwd as an implicit working tree".
We could do it by putting a special token into
GIT_WORK_TREE, but the obvious choice (an empty string) has
some portability problems.

Instead, we add a new boolean variable, GIT_IMPLICIT_WORK_TREE,
which suppresses the use of cwd as a working tree when
GIT_DIR is set. We trigger the new variable when we know we
are in a bare setting.

The variable is left intentionally undocumented, as this is
an internal detail (for now, anyway). If somebody comes up
with a good alternate use for it, and once we are confident
we have shaken any bugs out of it, we can consider promoting
it further.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>