Martin Koegler noted that create_delta() performs a new hash lookup
after every block copy encoding which are currently limited to 64KB.
In case of larger identical blocks, the next hash lookup would normally
point to the next 64KB block in the reference buffer and multiple block
copy operations will be consecutively encoded.
It is however possible that the reference buffer be sparsely indexed if
hash buckets have been trimmed down in create_delta_index() when hashing
of the reference buffer isn't well balanced. In that case the hash
lookup following a block copy might fail to match anything and the fact
that the reference buffer still matches beyond the previous 64KB block
will be missed.
Let's rework the code so that buffer comparison isn't bounded to 64KB
anymore. The match size should be as large as possible up front and
only then should multiple block copy be encoded to cover it all.
Also, fewer hash lookups will be performed in the end.
According to Martin, this patch should reduce his 92MB pack down to 75MB
with the dataset he has.
Tests performed on the Linux kernel repo show a slightly smaller pack and
a slightly faster repack.
Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
Not every input value passed to get_sha1 is an abbreviated SHA-1.
Its actually quite common for refs to be passed and for those
refs to resolve to full SHA-1s, in which case we may not need to
initialize the alternate object database list in this process.
I'm relocating the call to prepare_alt_odb closer to the code
that actually needs it to maintain the fix first introduced by
Junio in 99a19b43 (to avoid ambiguous SHA-1 abbreviations from
being accepted). This allows us to avoid the alt_odb list setup
if we won't actually need it.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
Calling getenv() is not that expensive, but its also not free,
and its certainly not cheaper than testing to see if alt_odb_tail
is not null.
Because we are calling prepare_alt_odb() from within find_sha1_file
every time we cannot find an object file locally we want to skip out
of prepare_alt_odb() as early as possible once we have initialized
our alternate list.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
In some repository configurations the user may have many packfiles,
but all of the recent commits/trees/tags/blobs are likely to
be in the most recent packfile (the one with the newest mtime).
It is therefore common to be able to complete an entire operation
by accessing only one packfile, even if there are 25 packfiles
available to the repository.
Rather than opening and mmaping the corresponding .idx file for
every pack found, we now only open and map the .idx when we suspect
there might be an object of interest in there.
Of course we cannot known in advance which packfile contains an
object, so we still need to scan the entire packed_git list to
locate anything. But odds are users want to access objects in the
most recently created packfiles first, and that may be all they
ever need for the current operation.
Junio observed in b867092f that placing recent packfiles before
older ones can slightly improve access times for recent objects,
without degrading it for historical object access.
This change improves upon Junio's observations by trying even harder
to avoid the .idx files that we won't need.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
This command can be used to initialize, update and inspect submodules. It
uses a .gitmodules file, readable by git-config, in the top level directory
of the 'superproject' to specify a mapping between submodule paths and
repository url.
With this entry in .gitmodules (and a commit reference in the index entry for
the path "git"), the command 'git submodule init' will clone the repository
at kernel.org into the directory "git".
Known issues
============
There is currently no way to override the url found in the .gitmodules file,
except by manually creating the subproject repository. The place to fix this
in the script has a rather long comment about a possible plan.
Funny paths will be quoted in the output from git-ls-files, but git-submodule
does not attempt to unquote (or even detect the presence of) such paths.
Signed-off-by: Lars Hjemli <hjemli@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>
This just basically creates a "pack_refs()" function that could be used by
anybody. You pass it in the flags you want as a bitmask (PACK_REFS_ALL and
PACK_REFS_PRUNE), and it will do all the heavy lifting.
Of course, it's still static, and it's all in the builtin-pack-refs.c
file, so it's not actually visible to the outside, but the next step would
be to just move it all to a library file (probably refs.c) and expose it.
Then we could easily make "git gc" do this too.
While I did it, I also made it check the return value of the fflush and
fsync stage, to make sure that we don't overwrite the old packed-refs file
with something that got truncated due to write errors!
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
* maint:
Fix git-svn to handle svn not reporting the md5sum of a file, and test.
Fix mishandling of $Id$ expanded in the repository copy in convert.c
More echo "$user_message" fixes.
Add tests for the last two fixes.
git-commit: use printf '%s\n' instead of echo on user-supplied strings
git-am: use printf instead of echo on user-supplied strings
Documentation: Add definition of "evil merge" to GIT Glossary
Replace the last 'dircache's by 'index'
Documentation: Clean up links in GIT Glossary
* maint-1.5.1:
Fix git-svn to handle svn not reporting the md5sum of a file, and test.
More echo "$user_message" fixes.
Add tests for the last two fixes.
git-commit: use printf '%s\n' instead of echo on user-supplied strings
git-am: use printf instead of echo on user-supplied strings
Documentation: Add definition of "evil merge" to GIT Glossary
Replace the last 'dircache's by 'index'
Documentation: Clean up links in GIT Glossary
This means that send-pack and http-push will support pattern refspecs,
so builtin-push.c doesn't have to expand them, and also git push can
just turn --tags into "refs/tags/*", further simplifying
builtin-push.c
check_ref_format() gets a third "conditionally okay" result for
something that's valid as a pattern but not as a particular ref.
Signed-off-by: Daniel Barkalow <barkalow@iabervon.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
Fix mishandling of $Id$ expanded in the repository copy in convert.c
If the repository contained an expanded ident keyword (i.e. $Id:XXXX$),
then the wrong bytes were discarded, and the Id keyword was not
expanded. The fault was in convert.c:ident_to_worktree().
Previously, when a "$Id:" was found in the repository version,
ident_to_worktree() would search for the next "$" after this, and
discarded everything it found until then. That was done with the loop:
do {
ch = *cp++;
if (ch == '$')
break;
rem--;
} while (rem);
The above loop left cp pointing one character _after_ the final "$"
(because of ch = *cp++). This was different from the non-expanded case,
were cp is left pointing at the "$", and was different from the comment
which stated "discard up to but not including the closing $". This
patch fixes that by making the loop:
do {
ch = *cp;
if (ch == '$')
break;
cp++;
rem--;
} while (rem);
That is, cp is tested _then_ incremented.
This loop exits if it finds a "$" or if it runs out of bytes in the
source. After this loop, if there was no closing "$" the expansion is
skipped, and the outer loop is allowed to continue leaving this
non-keyword as it was. However, when the "$" is found, size is
corrected, before running the expansion:
size -= (cp - src);
This is wrong; size is going to be corrected anyway after the expansion,
so there is no need to do it here. This patch removes that redundant
correction.
To help find this bug, I heavily commented the routine; those comments
are included here as a bonus.
Signed-off-by: Andy Parkins <andyparkins@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>
This updates t4014 to check the two fixes for git-am and git-commit
we observed with "echo" that does backslash interpolation by default
without being asked with -e option.
git-commit: use printf '%s\n' instead of echo on user-supplied strings
This fixes the same issue git-am had, which was fixed by Jeff
King in the previous commit. Cleverly enough, this commit's log
message is a good test case at the same time.
git-am: use printf instead of echo on user-supplied strings
Under some implementations of echo (such as that provided by
dash), backslash escapes are recognized without any other
options. This means that echo-ing user-supplied strings may
cause any backslash sequences in them to be converted. Using
printf resolves the ambiguity.
This bug can be seen when using git-am to apply a patch
whose subject contains the character sequence "\n"; the
characters are converted to a literal newline. Noticed by
Szekeres Istvan.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <junkio@cox.net>
Now that the default delta depth is 50, it is a good idea to also bump
MAX_CHAIN to 50.
While at it, make the display a bit prettier by making the MAX_CHAIN
limit inclusive, and display the number of deltas that are above that
limit at the end instead of the beginning.
Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
Add a configuration option to control diffstat after merge
The diffstat can be controlled either with command-line options
(--summary|--no-summary) or with merge.diffstat. The default is
left as it was: diffstat is active by default.
Signed-off-by: Alex Riesen <raa.lkml@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>
I believe noone uses git-applymbox, and noone definitely should, since it
is supposed to be completely superseded and everything by its younger
cousin git-am. The only known person in the universe to use it was Linus
and he declared some time ago that he will try to use git-am instead in his
famous dotest script.
The trouble is that git-applymbox existence creates confusing UI. I'm a bit
like a recycled newbie to the git porcelain and *I* was confused by
git-applymbox primitiveness until I've realized a while later that I'm of
course using the wrong command.
Signed-off-by: Petr Baudis <pasky@suse.cz> Signed-off-by: Junio C Hamano <junkio@cox.net>
* maint:
fix memory leak in parse_object when check_sha1_signature fails
name-rev: tolerate clock skew in committer dates
Update bash completion for git-config options
Teach bash completion about recent log long options
Teach bash completion about 'git remote update'
Update bash completion header documentation
Remove a duplicate --not option in bash completion
Teach bash completion about git-shortlog
Hide the plumbing diff-{files,index,tree} from bash completion
Update bash completion to ignore some more plumbing commands
Merge branch 'master' of git://repo.or.cz/git/fastimport into maint
* 'master' of git://repo.or.cz/git/fastimport:
Update bash completion for git-config options
Teach bash completion about recent log long options
Teach bash completion about 'git remote update'
Update bash completion header documentation
Remove a duplicate --not option in bash completion
Teach bash completion about git-shortlog
Hide the plumbing diff-{files,index,tree} from bash completion
Update bash completion to ignore some more plumbing commands
Ensure git-repack -a -d --max-pack-size=N deletes correct packs
The packfile portion of the "remove redundant" code
near the bottom of git-repack.sh is broken when
pack splitting occurs. Particularly since this is
the only place where we automatically delete packfiles,
make sure it works properly for all cases, old or new.
Signed-off-by: Dana L. How <danahow@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>
I've taught myself to use "git gc" instead of doing the repack explicitly,
but it doesn't actually do what I think it should do.
We've had packed refs for a long time now, and I think it just makes sense
to pack normal branches too. So I end up having to do
git pack-refs --all --prune
in order to get a nice git repo that doesn't have any unnecessary files.
So why not just do that in "git gc"? It's not as if there really is any
downside to packing branches, even if they end up changing later. Quite
often they don't, and even if they do, so what?
Also, make the default for refs packing just be an unambiguous "do it",
rather than "do it by default only for non-bare repositories". If you want
that behaviour, you can always just add a
[gc]
packrefs = notbare
in your ~/.gitconfig file, but I don't actually see why bare would be any
different (except for the broken reason that http-fetching used to be
totally broken, and not doing it just meant that it didn't even get
fixed in a timely manner!).
So here's a trivial patch to make "git gc" do a better job. Hmm?
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
fix memory leak in parse_object when check_sha1_signature fails
When check_sha1_signature fails, program is not terminated:
it prints an error message and returns NULL, so the
buffer returned by read_sha1_file should be freed before.
Signed-off-by: Carlos Rica <jasampler@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>
In git.git repository, "git-name-rev v1.3.0~158" cannot name the
rev, while adjacent revs can be named.
This was because it gives up traversal from the tips of existing
refs as soon as it sees a commit that has older commit timestamp
than what is being named. This is usually a good heuristics,
but v1.3.0~158 has a slightly older commit timestamp than
v1.3.0~157 (i.e. it's child), as these two were made in a
separate repostiory (in fact, in a different continent).
This adds a hardcoded slop value (1 day) to the cut-off
heuristics to work this kind of problem around. The current
algorithm essentially runs around from the available tips down
to ancient commits and names every single rev available that are
newer than cut-off date, so a single day slop would not add that
much overhead in repositories with long enough history where the
performance of name-rev matters.
I think the algorithm could be made a bit smarter by deepening
the graph on demand as a new commit is asked to be named (this
would require rewriting of name_rev() function not to recurse
itself but use a traversal list like revision.c traverser does),
but that would be a separate issue.
Acked-by: Johannes Schindelin <Johannes.Schindelin@gmx.de> Signed-off-by: Junio C Hamano <junkio@cox.net>
Alberto Bertogli reported on #git that git-gui was exiting with
alt-q, while gitk on the same system was exiting with ctrl-q.
That was not what I wanted. I really wanted M1B to be bound to
the Control key on most non-Mac OS X platforms, but according to
Sam Vilain M1 on most systems means alt. Since gitk always does
control, I'm doing the same thing for all non-Mac OS X systems.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
A few new configuration options grew out of the woodwork during the
1.5.2 series. Most of these are pretty easy to support a completion
of, so we do so.
I wanted to also add completion support for the <driver> part of
merge.<driver>.name but to do that we have to look at all of the
.gitattributes files and guess what the unique set of <driver>
strings would be. Since this appears to be non-trivial I'm punting
on it at this time.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Teach bash completion about recent log long options
(Somewhat) recently git-log learned about --reverse (to show commits
in the opposite order) and a looong time ago I think it learned
about --raw (to show the raw diff, rather than a unified diff).
These are both useful options, so we should make them easy for the
user to complete.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Recently the git-remote command grew an update subcommand, which
can be used to execute git-fetch across multiple repositories
in a single step. These can be configured with the 'remotes.*'
configuration options, so we can offer completion for any name that
matches and appears to be useful to git-remote update.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
1) Added a note about supporting the long options for most commands,
as we have been doing so for quite some time.
2) Include a notice that these routines are covered by the GPL,
as that may not be obvious, even though they are distributed
as part of the core Git distribution.
3) Added a short section on how to send patches to the routines,
and to whom they should get sent to. Currently that is me,
as I am the active maintainer.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Remove a duplicate --not option in bash completion
This was just me being silly; I put the --not option into the
completion list twice. There's no duplicates shown in the shell
as the shell removes them before showing them to the user. But we
really don't need the duplicates in the source script either.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
We've had completion for git-log for quite some time, but just
today I noticed we don't have it for the new builtin shortlog
that runs git-log internally. This is indeed a handy thing to
have completion for, especially when your branch names are of
the Very-Very-Long-and-Hard/To-Type/Variety/That-Some-Use.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Hide the plumbing diff-{files,index,tree} from bash completion
The diff-* programs are meant to be plumbing for the diff frontend;
most end users aren't invoking these commands directly. Consequently
we should avoid showing them as possible completions.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Fix possible coredump with fast-import --import-marks
When e8438420bb7d368bec3647b90c557b9931582267 allowed us to reload
the marks table on subsequent runs of fast-import we really broke
things, as we set pack_id to MAX_PACK_ID for any objects we imported
into the marks table. Creating a branch from that mark should fail
as we attempt to read the object through a non-existant packed_git
pointer. Instead we have to use the normal Git object system to
locate the older commit, as we ourselves do not have a reference
to the packed_git it resides in.
This bug only occurred because t9300 was not complete enough.
When we added the --import-marks feature we didn't actually test
its implementation enough to verify the function worked as intended.
I have corrected that, and included the changes as part of this fix.
Prior versions of fast-import fail the new test(s); this commit
allows them to pass.
Credit for this bug find goes to Simon Hausmann <simon@lst.de> as
he recently identified a similiar bug in the tree lazy-loading path.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Refactor fast-import branch creation from existing commit
To resolve a corner case uncovered by Simon Hausmann I need to
reuse the logic for the SHA-1 expression version of the 'from '
command within the mark version of the 'from ' command. This change
doesn't alter any functionality, but is merely breaking the common
code out to a function that I can reuse.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
fast-import: Fix crash when referencing already existing objects
Commit a5c1780a0355a71b9fb70f1f1977ce726ee5b8d8 sets the pack_id of existing
objects to MAX_PACK_ID. When the same object is referenced later again it is
found in the local object hash. With such a pack_id fast-import should not try
to locate that object in the newly created pack(s).
Signed-off-by: Simon Hausmann <simon@lst.de> Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
gitweb.perl - Optionally send archives as .zip files
git-archive already knows how to generate an archive as a tar or a zip
file, but gitweb did not. zip archvies are much more usable in a Windows
environment due to native support and this patch allows a site admin the
option to deliver zip rather than tar files. The selection is done by
inserting
Fix command line parameter parser of revert/cherry-pick
The parser was inconsistently done, in that it did not look at
the last command line parameter to see if it could be an unknown
option, although it was designed to notice unknown options if
they were given in positions the command expects to find them
(i.e. everything except the last parameter, which ought to be
<commit-ish>). This prevented a very natural invocation
builtin-pack-objects: remove unnecessary code for no-delta
As we do not consider objects marked as "no-delta" early, there
is no point to check if the other objects already in the delta
window are marked as such -- "no-delta" objects will not enter
the window to begin with.
git-gui: Tighten internal pattern match for lib/ directory
Our GITGUI_LIBDIR macro was testing only for @@ at the start of
the path, assuming nobody would ever find that to be a reasonable
prefix for a directory to install our library into. That is most
likely a valid assumption, but its even more unlikely they would
have the start be @@GITGUI_ and the end be @@. Note that we
cannot use the full string here because that would get expanded
by the sed replacement in our Makefile.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
While we can easily test the cvs <-> git-cvsserver
communication with :fork: and git-cvsserver server
there are some pserver specifics we should test, too.
Currently this are two tests of the pserver authentication.
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.de> Signed-off-by: Junio C Hamano <junkio@cox.net>
This teaches pack-objects to use .gitattributes mechanism so
that the user can specify certain blobs are not worth spending
CPU cycles to attempt deltification.
The name of the attrbute is "delta", and when it is set to
false, like this:
== .gitattributes ==
*.jpg -delta
they are always stored in the plain-compressed base object
representation.
pack-objects: pass fullname down to add_object_entry()
Instead of giving a hash for grouping, pass fullname to add_object_entry().
I want to add "do not try deltifying this object" bit to object_entry based on
the settings in .gitattributes, and hashing the name down too early would
interfere with that plan.
Often users want to know not which tagged version a commit came
after, but which tagged version a commit is contained within.
This latter task is the job of git-name-rev, but most users are
looking to git-describe to do the job.
Junio suggested we make `git describe --contains` run the correct
tool, `git name-rev`, and that's exactly what we do here. The output
of name-rev was adjusted slightly through the new --name-only option,
allowing describe to execv into name-rev and maintain its current
output format.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
git-apply: Fix removal of new trailing blank lines.
The earlier code removed one newline too many from the hunk that
adds new lines at the end of the file. Also the way the code
counted the added blank lines was somewhat roundabout; I think
the way updated code does it is more direct and easier to
follow:
* We keep track of the number of blank lines added;
* While processing each line, we notice if it adds a blank
line, and increment the counter, or reset it to zero
otherwise;
* When actually we apply the data, we remove the empty lines we
counted earlier if we are applying it at the end of the
file.
git-repack --max-pack-size: add option parsing to enable feature
Add --max-pack-size parsing and usage messages.
Upgrade git-repack.sh to handle multiple packfile names,
and build packfiles in GIT_OBJECT_DIRECTORY not GIT_DIR.
Update documentation.
Signed-off-by: Dana L. How <danahow@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>
git-repack --max-pack-size: split packs as asked by write_{object,one}()
Rewrite write_pack_file() to break to a new packfile
whenever write_object/write_one request it, and
correct the header's object count in the previous packfile.
Change write_index_file() to write an index
for just the objects in the most recent packfile.
Signed-off-by: Dana L. How <danahow@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>
With --max-pack-size, generate the appropriate write limit
for each object and check against it before each group of writes.
Update delta usability rules to handle base being in a previously-
written pack. Inline sha1write_compress() so we know the
exact size of the written data when it needs to be compressed.
Detect and return write "failure".
Signed-off-by: Dana L. How <danahow@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>
git-repack --max-pack-size: new file statics and code restructuring
Add "pack_size_limit", the limit specified by --max-pack-size,
"written_list", the list of objects written to the current pack,
and "nr_written", the number of objects in written_list.
Put "base_name" at file scope again and add forward declarations.
Move write_index_file() call from cnd_pack_objects() to
write_pack_file() since only the latter will know how
many times to call write_index_file().
Signed-off-by: Dana L. How <danahow@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>
Alter sha1close() 3rd argument to request flush only
update=0 suppressed writing the final SHA-1 but was not used.
Now final=0 suppresses SHA-1 finalization, SHA-1 writing,
and closing -- in other words, only flush the buffer.
Signed-off-by: Dana L. How <danahow@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>
Add an option to git-ls-tree to display also the size of blob
Add -l/--long option to git-ls-tree command, which displays
object size of a blob entry. Object size is placed after
object id (left-justified with minimum width of 7 characters).
For non-blob entries `-' is used.
Rationale: for non-blob entries size of an object has no much
meaning, and is not very interesting. Moreover, in planned
pack v4 tree objects would be constructed on demand, so tree
size would need to be calculated.
Signed-off-by: Jakub Narebski <jnareb@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>
This also adds a --remote option to send-pack, which specifies the
configured remote being used. It is provided automatically by
git-push, and must match the url (which is still needed, since there
could be multiple urls).
Signed-off-by: Daniel Barkalow <barkalow@iabervon.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
Move remote parsing into a library file out of builtin-push.
The new parser is different from the one in builtin-push in two ways:
the default is to use the current branch's remote, if there is one,
before "origin"; and config is used in preference to remotes.
Signed-off-by: Daniel Barkalow <barkalow@iabervon.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
This patch introduces --extended-regexp and --regexp-ignore-case options to
tune what kind of patterns the pattern-limiting options (--grep, --author,
...) accept.
Signed-off-by: Petr Baudis <pasky@suse.cz> Signed-off-by: Junio C Hamano <junkio@cox.net>
* maint:
annotate: make it work from subdirectories.
git-config: Correct asciidoc documentation for --int/--bool
t1300: Add tests for git-config --bool --get
unpack-trees.c: verify_uptodate: remove dead code
Use PATH_MAX instead of TEMPFILE_PATH_LEN
branch: fix segfault when resolving an invalid HEAD
* maint-1.5.1:
annotate: make it work from subdirectories.
git-config: Correct asciidoc documentation for --int/--bool
t1300: Add tests for git-config --bool --get
unpack-trees.c: verify_uptodate: remove dead code
Use PATH_MAX instead of TEMPFILE_PATH_LEN
branch: fix segfault when resolving an invalid HEAD