Re: [PATCH v2 02/11] merge-one-file: rewrite in C
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Sep 1, 2020, 21:06 UTC
- Message-ID
- <xmqqk0xdcim6.fsf@gitster.c.googlers.com>
- In-Reply-To
- <20200901105705.6059-3-alban.gruin@gmail.com>
Alban Gruin <alban.gruin@gmail.com> writes:
Show 52 quoted lines
> diff --git a/builtin/merge-one-file.c b/builtin/merge-one-file.c
> new file mode 100644
> index 0000000000..306a86c2f0
> --- /dev/null
> +++ b/builtin/merge-one-file.c
> @@ -0,0 +1,85 @@
> +/*
> + * Builtin "git merge-one-file"
> + *
> + * Copyright (c) 2020 Alban Gruin
> + *
> + * Based on git-merge-one-file.sh, written by Linus Torvalds.
> + *
> + * This is the git per-file merge utility, called with
> + *
> + * argv[1] - original file SHA1 (or empty)
> + * argv[2] - file in branch1 SHA1 (or empty)
> + * argv[3] - file in branch2 SHA1 (or empty)
> + * argv[4] - pathname in repository
> + * argv[5] - original file mode (or empty)
> + * argv[6] - file in branch1 mode (or empty)
> + * argv[7] - file in branch2 mode (or empty)
> + *
> + * Handle some trivial cases. The _really_ trivial cases have been
> + * handled already by git read-tree, but that one doesn't do any merges
> + * that might change the tree layout.
> + */
> +
> +#include "cache.h"
> +#include "builtin.h"
> +#include "lockfile.h"
> +#include "merge-strategies.h"
> +
> +static const char builtin_merge_one_file_usage[] =
> + "git merge-one-file <orig blob> <our blob> <their blob> <path> "
> + "<orig mode> <our mode> <their mode>\n\n"
> + "Blob ids and modes should be empty for missing files.";
> +
> +int cmd_merge_one_file(int argc, const char **argv, const char *prefix)
> +{
> + struct object_id orig_blob, our_blob, their_blob,
> + *p_orig_blob = NULL, *p_our_blob = NULL, *p_their_blob = NULL;
> + unsigned int orig_mode = 0, our_mode = 0, their_mode = 0, ret = 0;
> + struct lock_file lock = LOCK_INIT;
> +
> + if (argc != 8)
> + usage(builtin_merge_one_file_usage);
> +
> + if (repo_read_index(the_repository) < 0)
> + die("invalid index");
> +
> + repo_hold_locked_index(the_repository, &lock, LOCK_DIE_ON_ERROR);I do understand why we would want merge_strategies_one_file() helper introduced by this step so that the helper can work in an arbitrary repository (hence taking a pointer to repository structure as one of its parameters).
But the "merge-one-file" command will always work in the_repository. I do not see a point in using helpers that can work in an arbitrary repository, like repo_read_index() or repo_hold_locked_index(), in the above. I only see downsides --- it is longer to read, makes readers wonder if there is something tricky involving another repository going on, etc.
> + if (!get_oid(argv[1], &orig_blob)) {
> + p_orig_blob = &orig_blob;
> + orig_mode = strtol(argv[5], NULL, 8);Write a wrapper around strtol(...,...,8) to reduce repetition, and make sure you do not pass NULL as the second parameter to strtol() to always check you parsed the string to the end.
> + ret = merge_strategies_one_file(the_repository, > + p_orig_blob, p_our_blob, p_their_blob, argv[4], > + orig_mode, our_mode, their_mode);
Here, as I said above, it is perfectly fine to pass the_repository().
Show 6 quoted lines
> + if (ret) {
> + rollback_lock_file(&lock);
> + return ret;
> + }
> +
> + return write_locked_index(the_repository->index, &lock, COMMIT_LOCK);Likewise, I do not see much point in saying the_repository->index; the_index is a perfectly fine short-hand.
Show 77 quoted lines
> diff --git a/merge-strategies.c b/merge-strategies.c
> new file mode 100644
> index 0000000000..f2af4a894d
> --- /dev/null
> +++ b/merge-strategies.c
> @@ -0,0 +1,199 @@
> +#include "cache.h"
> +#include "dir.h"
> +#include "ll-merge.h"
> +#include "merge-strategies.h"
> +#include "xdiff-interface.h"
> +
> +static int add_to_index_cacheinfo(struct index_state *istate,
> + unsigned int mode,
> + const struct object_id *oid, const char *path)
> +{
> + struct cache_entry *ce;
> + int len, option;
> +
> + if (!verify_path(path, mode))
> + return error(_("Invalid path '%s'"), path);
> +
> + len = strlen(path);
> + ce = make_empty_cache_entry(istate, len);
> +
> + oidcpy(&ce->oid, oid);
> + memcpy(ce->name, path, len);
> + ce->ce_flags = create_ce_flags(0);
> + ce->ce_namelen = len;
> + ce->ce_mode = create_ce_mode(mode);
> + if (assume_unchanged)
> + ce->ce_flags |= CE_VALID;
> + option = ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE;
> + if (add_index_entry(istate, ce, option))
> + return error(_("%s: cannot add to the index"), path);
> +
> + return 0;
> +}
> +
> +static int checkout_from_index(struct index_state *istate, const char *path)
> +{
> + struct checkout state = CHECKOUT_INIT;
> + struct cache_entry *ce;
> +
> + state.istate = istate;
> + state.force = 1;
> + state.base_dir = "";
> + state.base_dir_len = 0;
> +
> + ce = index_file_exists(istate, path, strlen(path), 0);
> + if (checkout_entry(ce, &state, NULL, NULL) < 0)
> + return error(_("%s: cannot checkout file"), path);
> + return 0;
> +}
> +
> +static int merge_one_file_deleted(struct index_state *istate,
> + const struct object_id *orig_blob,
> + const struct object_id *our_blob,
> + const struct object_id *their_blob, const char *path,
> + unsigned int orig_mode, unsigned int our_mode, unsigned int their_mode)
> +{
> + if ((our_blob && orig_mode != our_mode) ||
> + (their_blob && orig_mode != their_mode))
> + return error(_("File %s deleted on one branch but had its "
> + "permissions changed on the other."), path);
> +
> + if (our_blob) {
> + printf(_("Removing %s\n"), path);
> +
> + if (file_exists(path))
> + remove_path(path);
> + }
> +
> + if (remove_file_from_index(istate, path))
> + return error("%s: cannot remove from the index", path);
> + return 0;
> +}These functions we see above all are now easy to write these days, thanks to the previous work that built many helpers to perform ommon operations (e.g. remove_path()). Reusing them is very good.
Show 40 quoted lines
> +static int do_merge_one_file(struct index_state *istate,
> + const struct object_id *orig_blob,
> + const struct object_id *our_blob,
> + const struct object_id *their_blob, const char *path,
> + unsigned int orig_mode, unsigned int our_mode, unsigned int their_mode)
> +{
> + int ret, i, dest;
> + mmbuffer_t result = {NULL, 0};
> + mmfile_t mmfs[3];
> + struct ll_merge_options merge_opts = {0};
> + struct cache_entry *ce;
> +
> + if (our_mode == S_IFLNK || their_mode == S_IFLNK)
> + return error(_("%s: Not merging symbolic link changes."), path);
> + else if (our_mode == S_IFGITLINK || their_mode == S_IFGITLINK)
> + return error(_("%s: Not merging conflicting submodule changes."), path);
> +
> + read_mmblob(mmfs + 1, our_blob);
> + read_mmblob(mmfs + 2, their_blob);
> +
> + if (orig_blob) {
> + printf(_("Auto-merging %s\n"), path);
> + read_mmblob(mmfs + 0, orig_blob);
> + } else {
> + printf(_("Added %s in both, but differently.\n"), path);
> + read_mmblob(mmfs + 0, &null_oid);
> + }
> +
> + merge_opts.xdl_opts = XDL_MERGE_ZEALOUS_ALNUM;
> + ret = ll_merge(&result, path,
> + mmfs + 0, "orig",
> + mmfs + 1, "our",
> + mmfs + 2, "their",
> + istate, &merge_opts);
> +
> + for (i = 0; i < 3; i++)
> + free(mmfs[i].ptr);
> +
> + if (ret > 127 || !orig_blob)
> + ret = error(_("content conflict in %s"), path);The original only checked if ret is zero or non-zero; here we require ret to be large. Intended?
ll_merge() that called ll_xdl_merge() (i.e. the most common case) would return the value returned from xdl_merge(), which can be -1 when we got an error before calling xdl_do_merge(). xdl_do_merge() in turn can return -1. The most common case returns the value returned from xdl_cleanup_merge(), which is 0 for clean merge, and any positive integer (not clipped to 127 or 128) for conflicted one.
> + /* Create the working tree file, using "our tree" version from > + the index, and then store the result of the merge. */
Style. (cf. Documentation/CodingGuidelines).
Show 7 quoted lines
> + ce = index_file_exists(istate, path, strlen(path), 0);
> + if (!ce)
> + BUG("file is not present in the cache?");
> +
> + unlink(path);
> + dest = open(path, O_WRONLY | O_CREAT, ce->ce_mode);
> + write_in_full(dest, result.ptr, result.size);If open() fails, we write to a bogus file descriptor here.
Show 9 quoted lines
> + close(dest);
> +
> + free(result.ptr);
> +
> + if (ret && our_mode != their_mode)
> + return error(_("permission conflict: %o->%o,%o in %s"),
> + orig_mode, our_mode, their_mode, path);
> + if (ret)
> + return 1;What is the error returning convention around here? Our usual convention is that 0 signals a success, and negative reports an error. Returning the value returned from add_file_to_index() below, and error() above, are consistent with the convention, but this one returns 1 that is not. When deviating from convention, it needs to be documented for the callers in a comment before the function definition.
> + > + return add_file_to_index(istate, path, 0); > +}
Show 57 quoted lines
> +int merge_strategies_one_file(struct repository *r,
> + const struct object_id *orig_blob,
> + const struct object_id *our_blob,
> + const struct object_id *their_blob, const char *path,
> + unsigned int orig_mode, unsigned int our_mode,
> + unsigned int their_mode)
> +{
> + if (orig_blob &&
> + ((!their_blob && our_blob && oideq(orig_blob, our_blob)) ||
> + (!our_blob && their_blob && oideq(orig_blob, their_blob))))
> + /* Deleted in both or deleted in one and unchanged in
> + the other */
> + return merge_one_file_deleted(r->index,
> + orig_blob, our_blob, their_blob, path,
> + orig_mode, our_mode, their_mode);
> + else if (!orig_blob && our_blob && !their_blob) {
> + /* Added in one. The other side did not add and we
> + added so there is nothing to be done, except making
> + the path merged. */
> + return add_to_index_cacheinfo(r->index, our_mode, our_blob, path);
> + } else if (!orig_blob && !our_blob && their_blob) {
> + printf(_("Adding %s\n"), path);
> +
> + if (file_exists(path))
> + return error(_("untracked %s is overwritten by the merge."), path);
> +
> + if (add_to_index_cacheinfo(r->index, their_mode, their_blob, path))
> + return 1;
> + return checkout_from_index(r->index, path);
> + } else if (!orig_blob && our_blob && their_blob &&
> + oideq(our_blob, their_blob)) {
> + /* Added in both, identically (check for same
> + permissions). */
> + if (our_mode != their_mode)
> + return error(_("File %s added identically in both branches, "
> + "but permissions conflict %o->%o."),
> + path, our_mode, their_mode);
> +
> + printf(_("Adding %s\n"), path);
> +
> + if (add_to_index_cacheinfo(r->index, our_mode, our_blob, path))
> + return 1;
> + return checkout_from_index(r->index, path);
> + } else if (our_blob && their_blob)
> + /* Modified in both, but differently. */
> + return do_merge_one_file(r->index,
> + orig_blob, our_blob, their_blob, path,
> + orig_mode, our_mode, their_mode);
> + else {
> + char *orig_hex = "", *our_hex = "", *their_hex = "";
> +
> + if (orig_blob)
> + orig_hex = oid_to_hex(orig_blob);
> + if (our_blob)
> + our_hex = oid_to_hex(our_blob);
> + if (their_blob)
> + their_hex = oid_to_hex(their_blob);Prepare three char [] buffers and use oid_to_hex_r() instead, instead of relying that we'd have sufficient number of entries in the rotating buffer.
Show 38 quoted lines
> + return error(_("%s: Not handling case %s -> %s -> %s"),
> + path, orig_hex, our_hex, their_hex);
> + }
> +
> + return 0;
> +}
> diff --git a/merge-strategies.h b/merge-strategies.h
> new file mode 100644
> index 0000000000..b527d145c7
> --- /dev/null
> +++ b/merge-strategies.h
> @@ -0,0 +1,13 @@
> +#ifndef MERGE_STRATEGIES_H
> +#define MERGE_STRATEGIES_H
> +
> +#include "object.h"
> +
> +int merge_strategies_one_file(struct repository *r,
> + const struct object_id *orig_blob,
> + const struct object_id *our_blob,
> + const struct object_id *their_blob, const char *path,
> + unsigned int orig_mode, unsigned int our_mode,
> + unsigned int their_mode);
> +
> +#endif /* MERGE_STRATEGIES_H */
> diff --git a/t/t6415-merge-dir-to-symlink.sh b/t/t6415-merge-dir-to-symlink.sh
> index 2eddcc7664..5fb74e39a0 100755
> --- a/t/t6415-merge-dir-to-symlink.sh
> +++ b/t/t6415-merge-dir-to-symlink.sh
> @@ -94,7 +94,7 @@ test_expect_success SYMLINKS 'a/b was resolved as symlink' '
> test -h a/b
> '
>
> -test_expect_failure 'do not lose untracked in merge (resolve)' '
> +test_expect_success 'do not lose untracked in merge (resolve)' '
> git reset --hard &&
> git checkout baseline^0 &&
> >a/b/c/e &&