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Revision cb99a34e23e32ca8e94bafaa9699cfd133a17fd3 authored by Derrick Stolee on 24 October 2019, 13:40:42 UTC, committed by Junio C Hamano on 25 October 2019, 02:19:16 UTC
The previous commit includes a failing test for an issue around fetch.writeCommitGraph and fetching in a repo with a submodule. Here, we fix that bug and set the test to "test_expect_success". The problem arises with this set of commands when the remote repo at <url> has a submodule. Note that --recurse-submodules is not needed to demonstrate the bug. $ git clone <url> test $ cd test $ git -c fetch.writeCommitGraph=true fetch origin Computing commit graph generation numbers: 100% (12/12), done. BUG: commit-graph.c:886: missing parent <hash1> for commit <hash2> Aborted (core dumped) As an initial fix, I converted the code in builtin/fetch.c that calls write_commit_graph_reachable() to instead launch a "git commit-graph write --reachable --split" process. That code worked, but is not how we want the feature to work long-term. That test did demonstrate that the issue must be something to do with internal state of the 'git fetch' process. The write_commit_graph() method in commit-graph.c ensures the commits we plan to write are "closed under reachability" using close_reachable(). This method walks from the input commits, and uses the UNINTERESTING flag to mark which commits have already been visited. This allows the walk to take O(N) time, where N is the number of commits, instead of O(P) time, where P is the number of paths. (The number of paths can be exponential in the number of commits.) However, the UNINTERESTING flag is used in lots of places in the codebase. This flag usually means some barrier to stop a commit walk, such as in revision-walking to compare histories. It is not often cleared after the walk completes because the starting points of those walks do not have the UNINTERESTING flag, and clear_commit_marks() would stop immediately. This is happening during a 'git fetch' call with a remote. The fetch negotiation is comparing the remote refs with the local refs and marking some commits as UNINTERESTING. I tested running clear_commit_marks_many() to clear the UNINTERESTING flag inside close_reachable(), but the tips did not have the flag, so that did nothing. It turns out that the calculate_changed_submodule_paths() method is at fault. Thanks, Peff, for pointing out this detail! More specifically, for each submodule, the collect_changed_submodules() runs a revision walk to essentially do file-history on the list of submodules. That revision walk marks commits UNININTERESTING if they are simplified away by not changing the submodule. Instead, I finally arrived on the conclusion that I should use a flag that is not used in any other part of the code. In commit-reach.c, a number of flags were defined for commit walk algorithms. The REACHABLE flag seemed like it made the most sense, and it seems it was not actually used in the file. The REACHABLE flag was used in early versions of commit-reach.c, but was removed by 4fbcca4 (commit-reach: make can_all_from_reach... linear, 2018-07-20). Add the REACHABLE flag to commit-graph.c and use it instead of UNINTERESTING in close_reachable(). This fixes the bug in manual testing. Reported-by: Johannes Schindelin <johannes.schindelin@gmx.de> Helped-by: Jeff King <peff@peff.net> Helped-by: Szeder Gábor <szeder.dev@gmail.com> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent e88aab9
merge-recursive.h
#ifndef MERGE_RECURSIVE_H
#define MERGE_RECURSIVE_H
#include "string-list.h"
#include "unpack-trees.h"
struct commit;
struct repository;
struct merge_options {
const char *ancestor;
const char *branch1;
const char *branch2;
enum {
MERGE_RECURSIVE_NORMAL = 0,
MERGE_RECURSIVE_OURS,
MERGE_RECURSIVE_THEIRS
} recursive_variant;
const char *subtree_shift;
unsigned buffer_output; /* 1: output at end, 2: keep buffered */
unsigned renormalize : 1;
long xdl_opts;
int verbosity;
int detect_directory_renames;
int diff_detect_rename;
int merge_detect_rename;
int diff_rename_limit;
int merge_rename_limit;
int rename_score;
int needed_rename_limit;
int show_rename_progress;
int call_depth;
struct strbuf obuf;
struct hashmap current_file_dir_set;
struct string_list df_conflict_file_set;
struct unpack_trees_options unpack_opts;
struct index_state orig_index;
struct repository *repo;
};
/*
* For dir_rename_entry, directory names are stored as a full path from the
* toplevel of the repository and do not include a trailing '/'. Also:
*
* dir: original name of directory being renamed
* non_unique_new_dir: if true, could not determine new_dir
* new_dir: final name of directory being renamed
* possible_new_dirs: temporary used to help determine new_dir; see comments
* in get_directory_renames() for details
*/
struct dir_rename_entry {
struct hashmap_entry ent; /* must be the first member! */
char *dir;
unsigned non_unique_new_dir:1;
struct strbuf new_dir;
struct string_list possible_new_dirs;
};
struct collision_entry {
struct hashmap_entry ent; /* must be the first member! */
char *target_file;
struct string_list source_files;
unsigned reported_already:1;
};
static inline int merge_detect_rename(struct merge_options *o)
{
return o->merge_detect_rename >= 0 ? o->merge_detect_rename :
o->diff_detect_rename >= 0 ? o->diff_detect_rename : 1;
}
/* merge_trees() but with recursive ancestor consolidation */
int merge_recursive(struct merge_options *o,
struct commit *h1,
struct commit *h2,
struct commit_list *ancestors,
struct commit **result);
/* rename-detecting three-way merge, no recursion */
int merge_trees(struct merge_options *o,
struct tree *head,
struct tree *merge,
struct tree *common,
struct tree **result);
/*
* "git-merge-recursive" can be fed trees; wrap them into
* virtual commits and call merge_recursive() proper.
*/
int merge_recursive_generic(struct merge_options *o,
const struct object_id *head,
const struct object_id *merge,
int num_ca,
const struct object_id **ca,
struct commit **result);
void init_merge_options(struct merge_options *o,
struct repository *repo);
struct tree *write_tree_from_memory(struct merge_options *o);
int parse_merge_opt(struct merge_options *out, const char *s);
#endif
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