blame $path: avoid getting fooled by case insensitive filesystems

"git blame MAKEFILE" run in a history that has "Makefile" but not
MAKEFILE can get confused on a case insensitive filesystem, because
the check we run to see if there is a corresponding file in the
working tree with lstat("MAKEFILE") succeeds.  In addition to that
check, we have to make sure that the given path also exists in the
commit we start digging history from (i.e. "HEAD").

Note that this reveals the breakage in a test added in cd8ae20
(git-blame shouldn't crash if run in an unmerged tree, 2007-10-18),
which expects the entire merge-in-progress path to be blamed to the
working tree when it did not exist in our tree.  As it is clear in
the log message of that commit, the old breakage was that it was
causing an internal error and the fix was about avoiding it.

Just check that the command does not die an uncontrolled death.  For
this particular case, the blame should fail, as the history for the
file in that contents has not been committed yet at the point in the
test.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
blame: allow "blame file" in the middle of a conflicted merge

"git blame file" has always meant "find the origin of each line of
the file in the history leading to HEAD, oh by the way, blame the
lines that are modified locally to the working tree".

This teaches "git blame" that during a conflicted merge, some
uncommitted changes may have come from the other history that is
being merged.

The verify_working_tree_path() function introduced in the previous
patch to notice a typo in the filename (primarily on case insensitive
filesystems) has been updated to allow a filename that does not exist
in HEAD (i.e. the tip of our history) as long as it exists one of the
commits being merged, so that a "we deleted, the other side modified"
case tracks the history of the file in the history of the other side.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
string_list: add function string_list_append_nodup()

Add a new function that appends a string to a string_list without
copying it.  This can be used to pass ownership of an already-copied
string to a string_list that has strdup_strings set.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
string_list: add two new functions for splitting strings

Add two new functions, string_list_split() and
string_list_split_in_place().  These split a string into a string_list
on a separator character.  The first makes copies of the substrings
(leaving the input string untouched) and the second splits the
original string in place, overwriting the separator characters with
NULs and referring to the original string's memory.

These functions are similar to the strbuf_split_*() functions except
that they work with the more powerful string_list interface.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
string_list: add a new function, filter_string_list()

This function allows entries that don't match a specified criterion to
be discarded from a string_list while preserving the order of the
remaining entries.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
string_list: add a new function, string_list_remove_duplicates()

Add a function that deletes duplicate entries from a sorted
string_list.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
string_list: add a function string_list_longest_prefix()

Add a function that finds the longest string from a string_list that
is a prefix of a given string.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
api-string-list.txt: initialize the string_list the easy way

In the demo code blurb, show how to initialize the string_list using
STRING_LIST_INIT_NODUP rather than memset().

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
t5500: add tests of error output for missing refs

If "git fetch-pack" is called with reference names that do not exist
on the remote, then it should emit an error message

    error: no such remote ref refs/heads/xyzzy

This is currently broken if *only* missing references are passed to
"git fetch-pack".

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
t5500: add tests of fetch-pack --all --depth=N $URL $REF

Document some bugs in "git fetch-pack":

1. If "git fetch-pack" is called with "--all", "--depth", and an
explicit existing non-tag reference to fetch, then it falsely reports
that the reference was not found, even though it was fetched
correctly.

2. If "git fetch-pack" is called with "--all", "--depth", and an
explicit existing tag reference to fetch, then it segfaults in
filter_refs() because return_refs is used without having been
initialized.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Rename static function fetch_pack() to http_fetch_pack()

Avoid confusion with the non-static function of the same name from
fetch-pack.h.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
fetch_pack(): reindent function decl and defn

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Change fetch_pack() and friends to take string_list arguments

Instead of juggling <nr_heads,heads> (sometimes called
<nr_match,match>), pass around the list of references to be sought in
a single string_list variable called "sought".  Future commits will
make more use of string_list functionality.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
filter_refs(): do not check the same sought_pos twice

Once a match has been found at sought_pos, the entry is zeroed and no
future attempts will match that entry.  So increment sought_pos to
avoid checking against the zeroed-out entry during the next iteration.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
fetch_pack(): update sought->nr to reflect number of unique entries

fetch_pack() removes duplicates from the "sought" list, thereby
shrinking the list.  But previously, the caller was not informed about
the shrinkage.  This would cause a spurious error message to be
emitted by cmd_fetch_pack() if "git fetch-pack" is called with
duplicate refnames.

Instead, remove duplicates using string_list_remove_duplicates(),
which adjusts sought->nr to reflect the new length of the list.

The last test of t5500 inexplicably *required* "git fetch-pack" to
fail when fetching a list of references that contains duplicates;
i.e., it insisted on the buggy behavior.  So change the test to expect
the correct behavior.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
filter_refs(): delete matched refs from sought list

Remove any references that are available from the remote from the
sought list (rather than overwriting their names with NUL characters,
as previously).  Mark matching entries by writing a non-NULL pointer
to string_list_item::util during the iteration, then use
filter_string_list() later to filter out the entries that have been
marked.

Document this aspect of fetch_pack() in a comment in the header file.
(More documentation is obviously still needed.)

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
filter_refs(): build refs list as we go

Instead of temporarily storing matched refs to temporary array
"return_refs", simply append them to newlist as we go.  This changes
the order of references in newlist to strictly sorted if "--all" and
"--depth" and named references are all specified, but that usage is
broken anyway (see the last two tests in t5500).

This changes the last test in t5500 from segfaulting into just
emitting a spurious error (this will be fixed in a moment).

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
filter_refs(): simplify logic

Simplify flow within loop: first decide whether to keep the reference,
then keep/free it.  This makes it clearer that each ref has exactly
two possible destinies, and removes duplication of the code for
appending the reference to the linked list.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
cmd_fetch_pack(): return early if finish_connect() fails

This simplifies the logic without changing the behavior.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
fetch-pack: report missing refs even if no existing refs were received

This fixes a test in t5500.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>