From: Phillip Wood Date: Wed, 10 Aug 2022 15:03:47 GMT Subject: Re: [PATCH v8 08/14] merge-resolve: rewrite in C Message-ID: <08ea1eec-58fb-cbfa-d405-0d4159c99515@gmail.com> In-Reply-To: <20220809185429.20098-9-alban.gruin@gmail.com> Hi Alban On 09/08/2022 19:54, Alban Gruin wrote: > This rewrites `git merge-resolve' from shell to C. As for `git > merge-one-file', this port is not completely straightforward and removes > calls to external processes to avoid reading and writing the index over > and over again. > > - The call to `update-index -q --refresh' is replaced by a call to > refresh_index(). > > - The call to `read-tree' is replaced by a call to unpack_trees() (and > all the setup needed). > > - The call to `write-tree' is replaced by a call to > cache_tree_update(). This call is wrapped in a new function, > write_tree(). It is made to mimick write_index_as_tree() with > WRITE_TREE_SILENT flag, but without locking the index; this is taken > care directly in merge_strategies_resolve(). > > - The call to `diff-index ...' is replaced by a call to > repo_index_has_changes(). > > - The call to `merge-index', needed to invoke `git merge-one-file', is > replaced by a call to the new merge_all_index() function. > > The index is read in cmd_merge_resolve(), and is wrote back by > merge_strategies_resolve(). This is to accomodate future applications: > in `git-merge', the index has already been read when the merge strategy > is called, so it would be redundant to read it again when the builtin > will be able to use merge_strategies_resolve() directly. > > The parameters of merge_strategies_resolve() will be surprising at first > glance: why using a commit list for `bases' and `remote', where we could > use an oid array, and a pointer to an oid? Because, in a later commit, > try_merge_strategy() will be able to call merge_strategies_resolve() > directly, and it already uses a commit list for `bases' (`common') and > `remote' (`remoteheads'), and a string for `head_arg'. To reduce > frictions later, merge_strategies_resolve() takes the same types of > parameters. git-merge-resolve will happily merge three trees, unfortunately using lists of commits will break that. > merge_strategies_resolve() locks the index only once, at the beginning > of the merge, and releases it when the merge has been completed. > > Signed-off-by: Alban Gruin > --- > diff --git a/builtin/merge-resolve.c b/builtin/merge-resolve.c > new file mode 100644 > index 0000000000..a51158ebf8 > --- /dev/null > +++ b/builtin/merge-resolve.c > @@ -0,0 +1,63 @@ > +/* > + * Builtin "git merge-resolve" > + * > + * Copyright (c) 2020 Alban Gruin > + * > + * Based on git-merge-resolve.sh, written by Linus Torvalds and Junio C > + * Hamano. > + * > + * Resolve two trees, using enhanced multi-base read-tree. > + */ > + > +#include "cache.h" > +#include "builtin.h" > +#include "merge-strategies.h" > + > +static const char builtin_merge_resolve_usage[] = > + "git merge-resolve ... -- "; > + > +int cmd_merge_resolve(int argc, const char **argv, const char *prefix) > +{ > + int i, sep_seen = 0; > + const char *head = NULL; > + struct commit_list *bases = NULL, *remote = NULL; > + struct commit_list **next_base = &bases; > + struct repository *r = the_repository; > + > + if (argc < 5) > + usage(builtin_merge_resolve_usage); I think it would be better to call parse_options() and then check argc. That would give better error messages for unknown options and supports '-h' for free. I think we also need to call git_config(). I see that read-tree respects submodule.recurse so I think we need the same here. I suspect we should also be reading the merge config to respect merge.conflictStyle. > + setup_work_tree(); > + if (repo_read_index(r) < 0) > + die("invalid index"); This should probably be marked for translation. > + > + /* > + * The first parameters up to -- are merge bases; the rest are > + * heads. > + */ > + for (i = 1; i < argc; i++) { > + if (!strcmp(argv[i], "--")) > + sep_seen = 1; > + else if (!strcmp(argv[i], "-h")) > + usage(builtin_merge_resolve_usage); > + else if (sep_seen && !head) > + head = argv[i]; > + else { > + struct object_id oid; > + struct commit *commit; > + > + if (get_oid(argv[i], &oid)) > + die("object %s not found.", argv[i]); translation here as well. > + commit = oideq(&oid, r->hash_algo->empty_tree) ? > + NULL : lookup_commit_or_die(&oid, argv[i]); As I said above, git-merge-resolve should be callable with trees I think. > + > + if (sep_seen) > + commit_list_insert(commit, &remote); > + else > + next_base = commit_list_append(commit, next_base); > + } > + } > + > + return merge_strategies_resolve(r, bases, head, remote); > +} > diff --git a/merge-strategies.c b/merge-strategies.c > index 373b69c10b..30f225ae5f 100644 > --- a/merge-strategies.c > +++ b/merge-strategies.c > @@ -1,9 +1,34 @@ > #include "cache.h" > +#include "cache-tree.h" > #include "dir.h" > #include "entry.h" > +#include "lockfile.h" > #include "merge-strategies.h" > +#include "unpack-trees.h" > #include "xdiff-interface.h" > > +static int check_index_is_head(struct repository *r, const char *head_arg) > +{ > + struct commit *head_commit; > + struct tree *head_tree; > + struct object_id head; > + struct strbuf sb = STRBUF_INIT; > + > + get_oid(head_arg, &head); > + head_commit = lookup_commit_reference(r, &head); > + head_tree = repo_get_commit_tree(r, head_commit); Can this all be replaced by a call to parse_tree_indirect(), we should also handle an invalid HEAD. > + > + if (repo_index_has_changes(r, head_tree, &sb)) { > + error(_("Your local changes to the following files " > + "would be overwritten by merge:\n %s"), > + sb.buf); This matches the script but I wonder why that did not check for unstaged changes. > +int merge_strategies_resolve(struct repository *r, > + struct commit_list *bases, const char *head_arg, As well as the commit vs tree comments above I think that we should be getting the callers to parse head rather than passing a string. Both builtin/merge.c and sequencer.c have a struct commit we can use. > + struct commit_list *remote) > +{ > + struct tree_desc t[MAX_UNPACK_TREES]; > + struct commit_list *i; > + struct lock_file lock = LOCK_INIT; > + int nr = 0, ret = 0; > + > + /* Abort if index does not match head */ > + if (check_index_is_head(r, head_arg)) > + return 2; > + > + /* > + * Give up if we are given two or more remotes. Not handling > + * octopus. > + */ > + if (remote && remote->next) > + return 2; > + > + /* Give up if this is a baseless merge. */ > + if (!bases) > + return 2; > + > + puts(_("Trying simple merge.")); > + > + for (i = bases; i && i->item; i = i->next) { > + if (add_tree(repo_get_commit_tree(r, i->item), t + (nr++))) This needs to check that we're not overrunning the end of t as builtin/read-tree.c:list_trees() does. Except for the tree issue the conversion of the script looks correct to me and you have been careful to preserve the exit values. Best Wishes Phillip > + return 2; > + } > + > + if (head_arg) { > + struct object_id head; > + struct tree *tree; > + > + get_oid(head_arg, &head); > + tree = parse_tree_indirect(&head); > + > + if (add_tree(tree, t + (nr++))) > + return 2; > + } > + > + if (remote && add_tree(repo_get_commit_tree(r, remote->item), t + (nr++))) > + return 2; > + > + repo_hold_locked_index(r, &lock, LOCK_DIE_ON_ERROR); > + > + if (merge_trees(r, t, nr, 1)) { > + rollback_lock_file(&lock); > + return 2; > + } > + > + if (write_tree(r)) { > + puts(_("Simple merge failed, trying Automatic merge.")); > + ret = merge_all_index(r->index, 1, 0, merge_one_file_func, NULL); > + } > + > + if (write_locked_index(r->index, &lock, COMMIT_LOCK)) > + return !!error(_("unable to write new index file")); > + return !!ret; > +} > diff --git a/merge-strategies.h b/merge-strategies.h > index 8705a550ca..bba4bf999c 100644 > --- a/merge-strategies.h > +++ b/merge-strategies.h > @@ -1,6 +1,7 @@ > #ifndef MERGE_STRATEGIES_H > #define MERGE_STRATEGIES_H > > +#include "commit.h" > #include "object.h" > > int merge_three_way(struct index_state *istate, > @@ -28,4 +29,8 @@ int merge_index_path(struct index_state *istate, int oneshot, int quiet, > int merge_all_index(struct index_state *istate, int oneshot, int quiet, > merge_fn fn, void *data); > > +int merge_strategies_resolve(struct repository *r, > + struct commit_list *bases, const char *head_arg, > + struct commit_list *remote); > + > #endif /* MERGE_STRATEGIES_H */