git/builtin/worktree.c, branch v2.16.2

Merge branch 'es/worktree-checkout-hook'

2017-12-27T19:16:21Z

"git worktree add" learned to run the post-checkout hook, just like "git checkout" does, after the initial checkout. * es/worktree-checkout-hook: worktree: invoke post-checkout hook (unless --no-checkout)

worktree: invoke post-checkout hook (unless --no-checkout)

2017-12-07T22:02:28Z

git-clone and git-checkout both invoke the post-checkout hook following a successful checkout, yet git-worktree neglects to do so even though it too "checks out" the worktree. Fix this oversight. Implementation note: The newly-created worktree may reference a branch or be detached. In the latter case, a commit lookup is performed, though the result is used only in a boolean sense to (a) determine if the commit actually exists, and (b) assign either the branch name or commit ID to HEAD. Since the post-commit hook needs to know the ID of the checked-out commit, the lookup now needs to be done in all cases, rather than only when detached. Consequently, a new boolean is needed to handle (b) since the lookup result itself can no longer perform that role. Reported-by: Matthew K Gumbel Signed-off-by: Eric Sunshine Signed-off-by: Junio C Hamano

add worktree.guessRemote config option

2017-12-06T17:47:35Z

Some users might want to have the --guess-remote option introduced in the previous commit on by default, so they don't have to type it out every time they create a new worktree. Add a config option worktree.guessRemote that allows users to configure the default behaviour for themselves. Signed-off-by: Thomas Gummerer Signed-off-by: Junio C Hamano

worktree: add --guess-remote flag to add subcommand

2017-12-06T17:47:35Z

Currently 'git worktree add ' creates a new branch named after the basename of the , that matches the HEAD of whichever worktree we were on when calling "git worktree add ". It's sometimes useful to have 'git worktree add behave more like the dwim machinery in 'git checkout ', i.e. check if the new branch name, derived from the basename of the , uniquely matches the branch name of a remote-tracking branch, and if so check out that branch and set the upstream to the remote-tracking branch. Add a new --guess-remote option that enables exactly that behaviour. Signed-off-by: Thomas Gummerer Signed-off-by: Junio C Hamano

worktree: make add dwim

2017-11-27T00:48:06Z

Currently 'git worktree add ', errors out when 'branch' is not a local branch. It has no additional dwim'ing features that one might expect. Make it behave more like 'git checkout ' when the branch doesn't exist locally, but a remote tracking branch uniquely matches the desired branch name, i.e. create a new branch from the remote tracking branch and set the upstream to the remote tracking branch. As 'git worktree add' currently just dies in this situation, there are no backwards compatibility worries when introducing this feature. Signed-off-by: Thomas Gummerer Signed-off-by: Junio C Hamano

worktree: add --[no-]track option to the add subcommand

2017-11-27T00:48:06Z

Currently 'git worktree add' sets up tracking branches if '' is a remote tracking branch, and doesn't set them up otherwise, as is the default for 'git branch'. This may or may not be what the user wants. Allow overriding this behaviour with a --[no-]track flag that gets passed through to 'git branch'. We already respect branch.autoSetupMerge, as 'git worktree' just calls 'git branch' internally. Signed-off-by: Thomas Gummerer Signed-off-by: Junio C Hamano

worktree: convert struct worktree to object_id

2017-10-16T02:05:51Z

Convert the head_sha1 member to be head_oid instead. This is required to convert resolve_ref_unsafe. Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano

worktree: check the result of read_in_full()

2017-09-27T06:46:05Z

We try to read "len" bytes into a buffer and just assume that it happened correctly. In practice this should usually be the case, since we just stat'd the file to get the length. But we could be fooled by transient errors or by other processes racily truncating the file. Let's be more careful. There's a slim chance this could catch a real error, but it also prevents people and tools from getting worried while reading the code. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

worktree: use xsize_t to access file size

2017-09-27T06:45:57Z

To read the "gitdir" file into memory, we stat the file and allocate a buffer. But we store the size in an "int", which may be truncated. We should use a size_t and xsize_t(), which will detect truncation. An overflow is unlikely for a "gitdir" file, but it's a good practice to model. Signed-off-by: Jeff King Reviewed-by: Jonathan Nieder Signed-off-by: Junio C Hamano

add UNLEAK annotation for reducing leak false positives

2017-09-08T06:43:17Z

It's a common pattern in git commands to allocate some memory that should last for the lifetime of the program and then not bother to free it, relying on the OS to throw it away. This keeps the code simple, and it's fast (we don't waste time traversing structures or calling free at the end of the program). But it also triggers warnings from memory-leak checkers like valgrind or LSAN. They know that the memory was still allocated at program exit, but they don't know _when_ the leaked memory stopped being useful. If it was early in the program, then it's probably a real and important leak. But if it was used right up until program exit, it's not an interesting leak and we'd like to suppress it so that we can see the real leaks. This patch introduces an UNLEAK() macro that lets us do so. To understand its design, let's first look at some of the alternatives. Unfortunately the suppression systems offered by leak-checking tools don't quite do what we want. A leak-checker basically knows two things: 1. Which blocks were allocated via malloc, and the callstack during the allocation. 2. Which blocks were left un-freed at the end of the program (and which are unreachable, but more on that later). Their suppressions work by mentioning the function or callstack of a particular allocation, and marking it as OK to leak. So imagine you have code like this: int cmd_foo(...) { /* this allocates some memory */ char *p = some_function(); printf("%s", p); return 0; } You can say "ignore allocations from some_function(), they're not leaks". But that's not right. That function may be called elsewhere, too, and we would potentially want to know about those leaks. So you can say "ignore the callstack when main calls some_function". That works, but your annotations are brittle. In this case it's only two functions, but you can imagine that the actual allocation is much deeper. If any of the intermediate code changes, you have to update the suppression. What we _really_ want to say is that "the value assigned to p at the end of the function is not a real leak". But leak-checkers can't understand that; they don't know about "p" in the first place. However, we can do something a little bit tricky if we make some assumptions about how leak-checkers work. They generally don't just report all un-freed blocks. That would report even globals which are still accessible when the leak-check is run. Instead they take some set of memory (like BSS) as a root and mark it as "reachable". Then they scan the reachable blocks for anything that looks like a pointer to a malloc'd block, and consider that block reachable. And then they scan those blocks, and so on, transitively marking anything reachable from a global as "not leaked" (or at least leaked in a different category). So we can mark the value of "p" as reachable by putting it into a variable with program lifetime. One way to do that is to just mark "p" as static. But that actually affects the run-time behavior if the function is called twice (you aren't likely to call main() twice, but some of our cmd_*() functions are called from other commands). Instead, we can trick the leak-checker by putting the value into _any_ reachable bytes. This patch keeps a global linked-list of bytes copied from "unleaked" variables. That list is reachable even at program exit, which confers recursive reachability on whatever values we unleak. In other words, you can do: int cmd_foo(...) { char *p = some_function(); printf("%s", p); UNLEAK(p); return 0; } to annotate "p" and suppress the leak report. But wait, couldn't we just say "free(p)"? In this toy example, yes. But UNLEAK()'s byte-copying strategy has several advantages over actually freeing the memory: 1. It's recursive across structures. In many cases our "p" is not just a pointer, but a complex struct whose fields may have been allocated by a sub-function. And in some cases (e.g., dir_struct) we don't even have a function which knows how to free all of the struct members. By marking the struct itself as reachable, that confers reachability on any pointers it contains (including those found in embedded structs, or reachable by walking heap blocks recursively. 2. It works on cases where we're not sure if the value is allocated or not. For example: char *p = argc > 1 ? argv[1] : some_function(); It's safe to use UNLEAK(p) here, because it's not freeing any memory. In the case that we're pointing to argv here, the reachability checker will just ignore our bytes. 3. Likewise, it works even if the variable has _already_ been freed. We're just copying the pointer bytes. If the block has been freed, the leak-checker will skip over those bytes as uninteresting. 4. Because it's not actually freeing memory, you can UNLEAK() before we are finished accessing the variable. This is helpful in cases like this: char *p = some_function(); return another_function(p); Writing this with free() requires: int ret; char *p = some_function(); ret = another_function(p); free(p); return ret; But with unleak we can just write: char *p = some_function(); UNLEAK(p); return another_function(p); This patch adds the UNLEAK() macro and enables it automatically when Git is compiled with SANITIZE=leak. In normal builds it's a noop, so we pay no runtime cost. It also adds some UNLEAK() annotations to show off how the feature works. On top of other recent leak fixes, these are enough to get t0000 and t0001 to pass when compiled with LSAN. Note the case in commit.c which actually converts a strbuf_release() into an UNLEAK. This code was already non-leaky, but the free didn't do anything useful, since we're exiting. Converting it to an annotation means that non-leak-checking builds pay no runtime cost. The cost is minimal enough that it's probably not worth going on a crusade to convert these kinds of frees to UNLEAKS. I did it here for consistency with the "sb" leak (though it would have been equally correct to go the other way, and turn them both into strbuf_release() calls). Signed-off-by: Jeff King Signed-off-by: Junio C Hamano