Merge branch 'jc/doc-reviewing-guidelines-positive-reviews' into next

[git.git] / sparse-index.c

#include "git-compat-util.h"
#include "environment.h"
#include "gettext.h"
#include "name-hash.h"
#include "read-cache-ll.h"
#include "repository.h"
#include "sparse-index.h"
#include "tree.h"
#include "pathspec.h"
#include "trace2.h"
#include "cache-tree.h"
#include "config.h"
#include "dir.h"
#include "fsmonitor-ll.h"
#include "advice.h"

/**
 * This global is used by expand_index() to determine if we should give the
 * advice for advice.sparseIndexExpanded when expanding a sparse index to a full
 * one. However, this is sometimes done on purpose, such as in the sparse-checkout
 * builtin, even when index.sparse=false. This may be disabled in
 * convert_to_sparse().
 */
static int give_advice_on_expansion = 1;
#define ADVICE_MSG \
        "The sparse index is expanding to a full index, a slow operation.\n"   \
        "Your working directory likely has contents that are outside of\n"     \
        "your sparse-checkout patterns. Use 'git sparse-checkout list' to\n"   \
        "see your sparse-checkout definition and compare it to your working\n" \
        "directory contents. Running 'git clean' may assist in this cleanup."

struct modify_index_context {
        struct index_state *write;
        struct pattern_list *pl;
};

static struct cache_entry *construct_sparse_dir_entry(
                                struct index_state *istate,
                                const char *sparse_dir,
                                struct cache_tree *tree)
{
        struct cache_entry *de;

        de = make_cache_entry(istate, S_IFDIR, &tree->oid, sparse_dir, 0, 0);

        de->ce_flags |= CE_SKIP_WORKTREE;
        return de;
}

/*
 * Returns the number of entries "inserted" into the index.
 */
static int convert_to_sparse_rec(struct index_state *istate,
                                 int num_converted,
                                 int start, int end,
                                 const char *ct_path, size_t ct_pathlen,
                                 struct cache_tree *ct)
{
        int i, can_convert = 1;
        int start_converted = num_converted;
        struct strbuf child_path = STRBUF_INIT;

        /*
         * Is the current path outside of the sparse cone?
         * Then check if the region can be replaced by a sparse
         * directory entry (everything is sparse and merged).
         */
        if (path_in_sparse_checkout(ct_path, istate))
                can_convert = 0;

        for (i = start; can_convert && i < end; i++) {
                struct cache_entry *ce = istate->cache[i];

                if (ce_stage(ce) ||
                    S_ISGITLINK(ce->ce_mode) ||
                    !(ce->ce_flags & CE_SKIP_WORKTREE))
                        can_convert = 0;
        }

        if (can_convert) {
                struct cache_entry *se;
                se = construct_sparse_dir_entry(istate, ct_path, ct);

                istate->cache[num_converted++] = se;
                return 1;
        }

        for (i = start; i < end; ) {
                int count, span, pos = -1;
                const char *base, *slash;
                struct cache_entry *ce = istate->cache[i];

                /*
                 * Detect if this is a normal entry outside of any subtree
                 * entry.
                 */
                base = ce->name + ct_pathlen;
                slash = strchr(base, '/');

                if (slash)
                        pos = cache_tree_subtree_pos(ct, base, slash - base);

                if (pos < 0) {
                        istate->cache[num_converted++] = ce;
                        i++;
                        continue;
                }

                strbuf_setlen(&child_path, 0);
                strbuf_add(&child_path, ce->name, slash - ce->name + 1);

                span = ct->down[pos]->cache_tree->entry_count;
                count = convert_to_sparse_rec(istate,
                                              num_converted, i, i + span,
                                              child_path.buf, child_path.len,
                                              ct->down[pos]->cache_tree);
                num_converted += count;
                i += span;
        }

        strbuf_release(&child_path);
        return num_converted - start_converted;
}

int set_sparse_index_config(struct repository *repo, int enable)
{
        int res = repo_config_set_worktree_gently(repo,
                                                  "index.sparse",
                                                  enable ? "true" : "false");
        prepare_repo_settings(repo);
        repo->settings.sparse_index = enable;
        return res;
}

static int index_has_unmerged_entries(struct index_state *istate)
{
        int i;
        for (i = 0; i < istate->cache_nr; i++) {
                if (ce_stage(istate->cache[i]))
                        return 1;
        }

        return 0;
}

int is_sparse_index_allowed(struct index_state *istate, int flags)
{
        if (!core_apply_sparse_checkout || !core_sparse_checkout_cone)
                return 0;

        if (!(flags & SPARSE_INDEX_MEMORY_ONLY)) {
                int test_env;

                /*
                 * The sparse index is not (yet) integrated with a split index.
                 */
                if (istate->split_index || git_env_bool("GIT_TEST_SPLIT_INDEX", 0))
                        return 0;
                /*
                 * The GIT_TEST_SPARSE_INDEX environment variable triggers the
                 * index.sparse config variable to be on.
                 */
                test_env = git_env_bool("GIT_TEST_SPARSE_INDEX", -1);
                if (test_env >= 0)
                        set_sparse_index_config(istate->repo, test_env);

                /*
                 * Only convert to sparse if index.sparse is set.
                 */
                prepare_repo_settings(istate->repo);
                if (!istate->repo->settings.sparse_index)
                        return 0;
        }

        if (init_sparse_checkout_patterns(istate))
                return 0;

        /*
         * We need cone-mode patterns to use sparse-index. If a user edits
         * their sparse-checkout file manually, then we can detect during
         * parsing that they are not actually using cone-mode patterns and
         * hence we need to abort this conversion _without error_. Warnings
         * already exist in the pattern parsing to inform the user of their
         * bad patterns.
         */
        if (!istate->sparse_checkout_patterns->use_cone_patterns)
                return 0;

        return 1;
}

int convert_to_sparse(struct index_state *istate, int flags)
{
        /*
         * If the index is already sparse, empty, or otherwise
         * cannot be converted to sparse, do not convert.
         */
        if (istate->sparse_index == INDEX_COLLAPSED || !istate->cache_nr ||
            !is_sparse_index_allowed(istate, flags))
                return 0;

        /*
         * If we are purposefully collapsing a full index, then don't give
         * advice when it is expanded later.
         */
        give_advice_on_expansion = 0;

        /*
         * NEEDSWORK: If we have unmerged entries, then stay full.
         * Unmerged entries prevent the cache-tree extension from working.
         */
        if (index_has_unmerged_entries(istate))
                return 0;

        if (!cache_tree_fully_valid(istate->cache_tree)) {
                /* Clear and recompute the cache-tree */
                cache_tree_free(&istate->cache_tree);

                /*
                 * Silently return if there is a problem with the cache tree update,
                 * which might just be due to a conflict state in some entry.
                 *
                 * This might create new tree objects, so be sure to use
                 * WRITE_TREE_MISSING_OK.
                 */
                if (cache_tree_update(istate, WRITE_TREE_MISSING_OK))
                        return 0;
        }

        remove_fsmonitor(istate);

        trace2_region_enter("index", "convert_to_sparse", istate->repo);
        istate->cache_nr = convert_to_sparse_rec(istate,
                                                 0, 0, istate->cache_nr,
                                                 "", 0, istate->cache_tree);

        /* Clear and recompute the cache-tree */
        cache_tree_free(&istate->cache_tree);
        cache_tree_update(istate, 0);

        istate->fsmonitor_has_run_once = 0;
        FREE_AND_NULL(istate->fsmonitor_dirty);
        FREE_AND_NULL(istate->fsmonitor_last_update);

        istate->sparse_index = INDEX_COLLAPSED;
        trace2_region_leave("index", "convert_to_sparse", istate->repo);
        return 0;
}

static void set_index_entry(struct index_state *istate, int nr, struct cache_entry *ce)
{
        ALLOC_GROW(istate->cache, nr + 1, istate->cache_alloc);

        istate->cache[nr] = ce;
        add_name_hash(istate, ce);
}

static int add_path_to_index(const struct object_id *oid,
                             struct strbuf *base, const char *path,
                             unsigned int mode, void *context)
{
        struct modify_index_context *ctx = (struct modify_index_context *)context;
        struct cache_entry *ce;
        size_t len = base->len;

        if (S_ISDIR(mode)) {
                int dtype;
                size_t baselen = base->len;
                if (!ctx->pl)
                        return READ_TREE_RECURSIVE;

                /*
                 * Have we expanded to a point outside of the sparse-checkout?
                 *
                 * Artificially pad the path name with a slash "/" to
                 * indicate it as a directory, and add an arbitrary file
                 * name ("-") so we can consider base->buf as a file name
                 * to match against the cone-mode patterns.
                 *
                 * If we compared just "path", then we would expand more
                 * than we should. Since every file at root is always
                 * included, we would expand every directory at root at
                 * least one level deep instead of using sparse directory
                 * entries.
                 */
                strbuf_addstr(base, path);
                strbuf_add(base, "/-", 2);

                if (path_matches_pattern_list(base->buf, base->len,
                                              NULL, &dtype,
                                              ctx->pl, ctx->write)) {
                        strbuf_setlen(base, baselen);
                        return READ_TREE_RECURSIVE;
                }

                /*
                 * The path "{base}{path}/" is a sparse directory. Create the correct
                 * name for inserting the entry into the index.
                 */
                strbuf_setlen(base, base->len - 1);
        } else {
                strbuf_addstr(base, path);
        }

        ce = make_cache_entry(ctx->write, mode, oid, base->buf, 0, 0);
        ce->ce_flags |= CE_SKIP_WORKTREE | CE_EXTENDED;
        set_index_entry(ctx->write, ctx->write->cache_nr++, ce);

        strbuf_setlen(base, len);
        return 0;
}

void expand_index(struct index_state *istate, struct pattern_list *pl)
{
        int i;
        struct index_state *full;
        struct strbuf base = STRBUF_INIT;
        const char *tr_region;
        struct modify_index_context ctx;

        /*
         * If the index is already full, then keep it full. We will convert
         * it to a sparse index on write, if possible.
         */
        if (istate->sparse_index == INDEX_EXPANDED)
                return;

        /*
         * If our index is sparse, but our new pattern set does not use
         * cone mode patterns, then we need to expand the index before we
         * continue. A NULL pattern set indicates a full expansion to a
         * full index.
         */
        if (pl && !pl->use_cone_patterns) {
                pl = NULL;
        } else {
                /*
                 * We might contract file entries into sparse-directory
                 * entries, and for that we will need the cache tree to
                 * be recomputed.
                 */
                cache_tree_free(&istate->cache_tree);

                /*
                 * If there is a problem creating the cache tree, then we
                 * need to expand to a full index since we cannot satisfy
                 * the current request as a sparse index.
                 */
                if (cache_tree_update(istate, 0))
                        pl = NULL;
        }

        if (!pl && give_advice_on_expansion) {
                give_advice_on_expansion = 0;
                advise_if_enabled(ADVICE_SPARSE_INDEX_EXPANDED,
                                  _(ADVICE_MSG));
        }

        /*
         * A NULL pattern set indicates we are expanding a full index, so
         * we use a special region name that indicates the full expansion.
         * This is used by test cases, but also helps to differentiate the
         * two cases.
         */
        tr_region = pl ? "expand_index" : "ensure_full_index";
        trace2_region_enter("index", tr_region, istate->repo);

        /* initialize basics of new index */
        full = xcalloc(1, sizeof(struct index_state));
        memcpy(full, istate, sizeof(struct index_state));

        /*
         * This slightly-misnamed 'full' index might still be sparse if we
         * are only modifying the list of sparse directories. This hinges
         * on whether we have a non-NULL pattern list.
         */
        full->sparse_index = pl ? INDEX_PARTIALLY_SPARSE : INDEX_EXPANDED;

        /* then change the necessary things */
        full->cache_alloc = (3 * istate->cache_alloc) / 2;
        full->cache_nr = 0;
        ALLOC_ARRAY(full->cache, full->cache_alloc);

        ctx.write = full;
        ctx.pl = pl;

        for (i = 0; i < istate->cache_nr; i++) {
                struct cache_entry *ce = istate->cache[i];
                struct tree *tree;
                struct pathspec ps;
                int dtype;

                if (!S_ISSPARSEDIR(ce->ce_mode)) {
                        set_index_entry(full, full->cache_nr++, ce);
                        continue;
                }

                /* We now have a sparse directory entry. Should we expand? */
                if (pl &&
                    path_matches_pattern_list(ce->name, ce->ce_namelen,
                                              NULL, &dtype,
                                              pl, istate) == NOT_MATCHED) {
                        set_index_entry(full, full->cache_nr++, ce);
                        continue;
                }

                if (!(ce->ce_flags & CE_SKIP_WORKTREE))
                        warning(_("index entry is a directory, but not sparse (%08x)"),
                                ce->ce_flags);

                /* recursively walk into cd->name */
                tree = lookup_tree(istate->repo, &ce->oid);

                memset(&ps, 0, sizeof(ps));
                ps.recursive = 1;
                ps.has_wildcard = 1;
                ps.max_depth = -1;

                strbuf_setlen(&base, 0);
                strbuf_add(&base, ce->name, strlen(ce->name));

                read_tree_at(istate->repo, tree, &base, 0, &ps,
                             add_path_to_index, &ctx);

                /* free directory entries. full entries are re-used */
                discard_cache_entry(ce);
        }

        /* Copy back into original index. */
        memcpy(&istate->name_hash, &full->name_hash, sizeof(full->name_hash));
        memcpy(&istate->dir_hash, &full->dir_hash, sizeof(full->dir_hash));
        istate->sparse_index = pl ? INDEX_PARTIALLY_SPARSE : INDEX_EXPANDED;
        free(istate->cache);
        istate->cache = full->cache;
        istate->cache_nr = full->cache_nr;
        istate->cache_alloc = full->cache_alloc;
        istate->fsmonitor_has_run_once = 0;
        FREE_AND_NULL(istate->fsmonitor_dirty);
        FREE_AND_NULL(istate->fsmonitor_last_update);

        strbuf_release(&base);
        free(full);

        /* Clear and recompute the cache-tree */
        cache_tree_free(&istate->cache_tree);
        cache_tree_update(istate, 0);

        trace2_region_leave("index", tr_region, istate->repo);
}

void ensure_full_index(struct index_state *istate)
{
        if (!istate)
                BUG("ensure_full_index() must get an index!");
        expand_index(istate, NULL);
}

void ensure_correct_sparsity(struct index_state *istate)
{
        /*
         * If the index can be sparse, make it sparse. Otherwise,
         * ensure the index is full.
         */
        if (is_sparse_index_allowed(istate, 0))
                convert_to_sparse(istate, 0);
        else
                ensure_full_index(istate);
}

struct path_found_data {
        /**
         * The path stored in 'dir', if non-empty, corresponds to the most-
         * recent path that we checked where:
         *
         *   1. The path should be a directory, according to the index.
         *   2. The path does not exist.
         *   3. The parent path _does_ exist. (This may be the root of the
         *      working directory.)
         */
        struct strbuf dir;
        size_t lstat_count;
};

#define PATH_FOUND_DATA_INIT { \
        .dir = STRBUF_INIT \
}

static void clear_path_found_data(struct path_found_data *data)
{
        strbuf_release(&data->dir);
}

/**
 * Return the length of the longest common substring that ends in a
 * slash ('/') to indicate the longest common parent directory. Returns
 * zero if no common directory exists.
 */
static size_t max_common_dir_prefix(const char *path1, const char *path2)
{
        size_t common_prefix = 0;
        for (size_t i = 0; path1[i] && path2[i]; i++) {
                if (path1[i] != path2[i])
                        break;

                /*
                 * If they agree at a directory separator, then add one
                 * to make sure it is included in the common prefix string.
                 */
                if (path1[i] == '/')
                        common_prefix = i + 1;
        }

        return common_prefix;
}

static int path_found(const char *path, struct path_found_data *data)
{
        struct stat st;
        size_t common_prefix;

        /*
         * If data->dir is non-empty, then it contains a path that doesn't
         * exist, including an ending slash ('/'). If it is a prefix of 'path',
         * then we can return 0.
         */
        if (data->dir.len && !memcmp(path, data->dir.buf, data->dir.len))
                return 0;

        /*
         * Otherwise, we must check if the current path exists. If it does, then
         * return 1. The cached directory will be skipped until we come across
         * a missing path again.
         */
        data->lstat_count++;
        if (!lstat(path, &st))
                return 1;

        /*
         * At this point, we know that 'path' doesn't exist, and we know that
         * the parent directory of 'data->dir' does exist. Let's set 'data->dir'
         * to be the top-most non-existing directory of 'path'. If the first
         * parent of 'path' exists, then we will act as though 'path'
         * corresponds to a directory (by adding a slash).
         */
        common_prefix = max_common_dir_prefix(path, data->dir.buf);

        /*
         * At this point, 'path' and 'data->dir' have a common existing parent
         * directory given by path[0..common_prefix] (which could have length 0).
         * We "grow" the data->dir buffer by checking for existing directories
         * along 'path'.
         */

        strbuf_setlen(&data->dir, common_prefix);
        while (1) {
                /* Find the next directory in 'path'. */
                const char *rest = path + data->dir.len;
                const char *next_slash = strchr(rest, '/');

                /*
                 * If there are no more slashes, then 'path' doesn't contain a
                 * non-existent _parent_ directory. Set 'data->dir' to be equal
                 * to 'path' plus an additional slash, so it can be used for
                 * caching in the future. The filename of 'path' is considered
                 * a non-existent directory.
                 *
                 * Note: if "{path}/" exists as a directory, then it will never
                 * appear as a prefix of other callers to this method, assuming
                 * the context from the clear_skip_worktree... methods. If this
                 * method is reused, then this must be reconsidered.
                 */
                if (!next_slash) {
                        strbuf_addstr(&data->dir, rest);
                        strbuf_addch(&data->dir, '/');
                        break;
                }

                /*
                 * Now that we have a slash, let's grow 'data->dir' to include
                 * this slash, then test if we should stop.
                 */
                strbuf_add(&data->dir, rest, next_slash - rest + 1);

                /* If the parent dir doesn't exist, then stop here. */
                data->lstat_count++;
                if (lstat(data->dir.buf, &st))
                        return 0;
        }

        /*
         * At this point, 'data->dir' is equal to 'path' plus a slash character,
         * and the parent directory of 'path' definitely exists. Moreover, we
         * know that 'path' doesn't exist, or we would have returned 1 earlier.
         */
        return 0;
}

static int clear_skip_worktree_from_present_files_sparse(struct index_state *istate)
{
        struct path_found_data data = PATH_FOUND_DATA_INIT;

        int path_count = 0;
        int to_restart = 0;

        trace2_region_enter("index", "clear_skip_worktree_from_present_files_sparse",
                            istate->repo);
        for (int i = 0; i < istate->cache_nr; i++) {
                struct cache_entry *ce = istate->cache[i];

                if (ce_skip_worktree(ce)) {
                        path_count++;
                        if (path_found(ce->name, &data)) {
                                if (S_ISSPARSEDIR(ce->ce_mode)) {
                                        to_restart = 1;
                                        break;
                                }
                                ce->ce_flags &= ~CE_SKIP_WORKTREE;
                        }
                }
        }

        trace2_data_intmax("index", istate->repo,
                           "sparse_path_count", path_count);
        trace2_data_intmax("index", istate->repo,
                           "sparse_lstat_count", data.lstat_count);
        trace2_region_leave("index", "clear_skip_worktree_from_present_files_sparse",
                            istate->repo);
        clear_path_found_data(&data);
        return to_restart;
}

static void clear_skip_worktree_from_present_files_full(struct index_state *istate)
{
        struct path_found_data data = PATH_FOUND_DATA_INIT;

        int path_count = 0;

        trace2_region_enter("index", "clear_skip_worktree_from_present_files_full",
                            istate->repo);
        for (int i = 0; i < istate->cache_nr; i++) {
                struct cache_entry *ce = istate->cache[i];

                if (S_ISSPARSEDIR(ce->ce_mode))
                        BUG("ensure-full-index did not fully flatten?");

                if (ce_skip_worktree(ce)) {
                        path_count++;
                        if (path_found(ce->name, &data))
                                ce->ce_flags &= ~CE_SKIP_WORKTREE;
                }
        }

        trace2_data_intmax("index", istate->repo,
                           "full_path_count", path_count);
        trace2_data_intmax("index", istate->repo,
                           "full_lstat_count", data.lstat_count);
        trace2_region_leave("index", "clear_skip_worktree_from_present_files_full",
                            istate->repo);
        clear_path_found_data(&data);
}

void clear_skip_worktree_from_present_files(struct index_state *istate)
{
        if (!core_apply_sparse_checkout ||
            sparse_expect_files_outside_of_patterns)
                return;

        if (clear_skip_worktree_from_present_files_sparse(istate)) {
                ensure_full_index(istate);
                clear_skip_worktree_from_present_files_full(istate);
        }
}

/*
 * This static global helps avoid infinite recursion between
 * expand_to_path() and index_file_exists().
 */
static int in_expand_to_path = 0;

void expand_to_path(struct index_state *istate,
                    const char *path, size_t pathlen, int icase)
{
        struct strbuf path_mutable = STRBUF_INIT;
        size_t substr_len;

        /* prevent extra recursion */
        if (in_expand_to_path)
                return;

        if (!istate->sparse_index)
                return;

        in_expand_to_path = 1;

        /*
         * We only need to actually expand a region if the
         * following are both true:
         *
         * 1. 'path' is not already in the index.
         * 2. Some parent directory of 'path' is a sparse directory.
         */

        if (index_file_exists(istate, path, pathlen, icase))
                goto cleanup;

        strbuf_add(&path_mutable, path, pathlen);
        strbuf_addch(&path_mutable, '/');

        /* Check the name hash for all parent directories */
        substr_len = 0;
        while (substr_len < pathlen) {
                char temp;
                char *replace = strchr(path_mutable.buf + substr_len, '/');

                if (!replace)
                        break;

                /* replace the character _after_ the slash */
                replace++;
                temp = *replace;
                *replace = '\0';
                substr_len = replace - path_mutable.buf;
                if (index_file_exists(istate, path_mutable.buf,
                                      substr_len, icase)) {
                        /*
                         * We found a parent directory in the name-hash
                         * hashtable, because only sparse directory entries
                         * have a trailing '/' character.  Since "path" wasn't
                         * in the index, perhaps it exists within this
                         * sparse-directory.  Expand accordingly.
                         */
                        ensure_full_index(istate);
                        break;
                }

                *replace = temp;
        }

cleanup:
        strbuf_release(&path_mutable);
        in_expand_to_path = 0;
}