backfill: add --sparse option
One way to significantly reduce the cost of a Git clone and later fetches is to use a blobless partial clone and combine that with a sparse-checkout that reduces the paths that need to be populated in the working directory. Not only does this reduce the cost of clones and fetches, the sparse-checkout reduces the number of objects needed to download from a promisor remote. However, history investigations can be expensive as computing blob diffs will trigger promisor remote requests for one object at a time. This can be avoided by downloading the blobs needed for the given sparse-checkout using 'git backfill' and its new '--sparse' mode, at a time that the user is willing to pay that extra cost. Note that this is distinctly different from the '--filter=sparse:<oid>' option, as this assumes that the partial clone has all reachable trees and we are using client-side logic to avoid downloading blobs outside of the sparse-checkout cone. This avoids the server-side cost of walking trees while also achieving a similar goal. It also downloads in batches based on similar path names, presenting a resumable download if things are interrupted. This augments the path-walk API to have a possibly-NULL 'pl' member that may point to a 'struct pattern_list'. This could be more general than the sparse-checkout definition at HEAD, but 'git backfill --sparse' is currently the only consumer. Be sure to test this in both cone mode and not cone mode. Cone mode has the benefit that the path-walk can skip certain paths once they would expand beyond the sparse-checkout. Non-cone mode can describe the included files using both positive and negative patterns, which changes the possible return values of path_matches_pattern_list(). Test both kinds of matches for increased coverage. To test this, we can create a blobless sparse clone, expand the sparse-checkout slightly, and then run 'git backfill --sparse' to see how much data is downloaded. The general steps are 1. git clone --filter=blob:none --sparse <url> 2. git sparse-checkout set <dir1> ... <dirN> 3. git backfill --sparse For the Git repository with the 'builtin' directory in the sparse-checkout, we get these results for various batch sizes: | Batch Size | Pack Count | Pack Size | Time | |-----------------|------------|-----------|-------| | (Initial clone) | 3 | 110 MB | | | 10K | 12 | 192 MB | 17.2s | | 15K | 9 | 192 MB | 15.5s | | 20K | 8 | 192 MB | 15.5s | | 25K | 7 | 192 MB | 14.7s | This case matters less because a full clone of the Git repository from GitHub is currently at 277 MB. Using a copy of the Linux repository with the 'kernel/' directory in the sparse-checkout, we get these results: | Batch Size | Pack Count | Pack Size | Time | |-----------------|------------|-----------|------| | (Initial clone) | 2 | 1,876 MB | | | 10K | 11 | 2,187 MB | 46s | | 25K | 7 | 2,188 MB | 43s | | 50K | 5 | 2,194 MB | 44s | | 100K | 4 | 2,194 MB | 48s | This case is more meaningful because a full clone of the Linux repository is currently over 6 GB, so this is a valuable way to download a fraction of the repository and no longer need network access for all reachable objects within the sparse-checkout. Choosing a batch size will depend on a lot of factors, including the user's network speed or reliability, the repository's file structure, and how many versions there are of the file within the sparse-checkout scope. There will not be a one-size-fits-all solution. Signed-off-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>maint
Derrick Stolee
Junio C Hamano
parent
6840fe9ee2
commit
bff4555767
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@ -9,7 +9,7 @@ git-backfill - Download missing objects in a partial clone
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SYNOPSIS
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--------
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[synopsis]
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git backfill [--min-batch-size=<n>]
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git backfill [--min-batch-size=<n>] [--[no-]sparse]
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DESCRIPTION
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-----------
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@ -57,6 +57,10 @@ OPTIONS
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blobs seen at a given path. The default minimum batch size is
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50,000.
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`--[no-]sparse`::
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Only download objects if they appear at a path that matches the
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current sparse-checkout.
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SEE ALSO
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--------
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linkgit:git-clone[1].
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@ -56,6 +56,14 @@ better off using the revision walk API instead.
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the revision walk so that the walk emits commits marked with the
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`UNINTERESTING` flag.
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`pl`::
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This pattern list pointer allows focusing the path-walk search to
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a set of patterns, only emitting paths that match the given
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patterns. See linkgit:gitignore[5] or
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linkgit:git-sparse-checkout[1] for details about pattern lists.
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When the pattern list uses cone-mode patterns, then the path-walk
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API can prune the set of paths it walks to improve performance.
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Examples
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--------
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@ -4,6 +4,7 @@
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#include "parse-options.h"
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#include "repository.h"
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#include "commit.h"
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#include "dir.h"
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#include "hex.h"
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#include "tree.h"
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#include "tree-walk.h"
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@ -21,7 +22,7 @@
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#include "path-walk.h"
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static const char * const builtin_backfill_usage[] = {
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N_("git backfill [--min-batch-size=<n>]"),
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N_("git backfill [--min-batch-size=<n>] [--[no-]sparse]"),
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NULL
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};
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@ -29,6 +30,7 @@ struct backfill_context {
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struct repository *repo;
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struct oid_array current_batch;
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size_t min_batch_size;
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int sparse;
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};
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static void backfill_context_clear(struct backfill_context *ctx)
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@ -78,6 +80,14 @@ static int do_backfill(struct backfill_context *ctx)
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struct path_walk_info info = PATH_WALK_INFO_INIT;
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int ret;
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if (ctx->sparse) {
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CALLOC_ARRAY(info.pl, 1);
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if (get_sparse_checkout_patterns(info.pl)) {
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path_walk_info_clear(&info);
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return error(_("problem loading sparse-checkout"));
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}
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}
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repo_init_revisions(ctx->repo, &revs, "");
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handle_revision_arg("HEAD", &revs, 0, 0);
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@ -106,10 +116,13 @@ int cmd_backfill(int argc, const char **argv, const char *prefix, struct reposit
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.repo = repo,
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.current_batch = OID_ARRAY_INIT,
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.min_batch_size = 50000,
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.sparse = 0,
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};
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struct option options[] = {
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OPT_INTEGER(0, "min-batch-size", &ctx.min_batch_size,
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N_("Minimum number of objects to request at a time")),
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OPT_BOOL(0, "sparse", &ctx.sparse,
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N_("Restrict the missing objects to the current sparse-checkout")),
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OPT_END(),
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};
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10
dir.c
10
dir.c
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@ -1093,10 +1093,6 @@ static void invalidate_directory(struct untracked_cache *uc,
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dir->dirs[i]->recurse = 0;
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}
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static int add_patterns_from_buffer(char *buf, size_t size,
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const char *base, int baselen,
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struct pattern_list *pl);
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/* Flags for add_patterns() */
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#define PATTERN_NOFOLLOW (1<<0)
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@ -1186,9 +1182,9 @@ static int add_patterns(const char *fname, const char *base, int baselen,
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return 0;
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}
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static int add_patterns_from_buffer(char *buf, size_t size,
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const char *base, int baselen,
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struct pattern_list *pl)
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int add_patterns_from_buffer(char *buf, size_t size,
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const char *base, int baselen,
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struct pattern_list *pl)
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{
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char *orig = buf;
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int i, lineno = 1;
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3
dir.h
3
dir.h
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@ -467,6 +467,9 @@ void add_patterns_from_file(struct dir_struct *, const char *fname);
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int add_patterns_from_blob_to_list(struct object_id *oid,
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const char *base, int baselen,
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struct pattern_list *pl);
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int add_patterns_from_buffer(char *buf, size_t size,
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const char *base, int baselen,
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struct pattern_list *pl);
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void parse_path_pattern(const char **string, int *patternlen, unsigned *flags, int *nowildcardlen);
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void add_pattern(const char *string, const char *base,
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int baselen, struct pattern_list *pl, int srcpos);
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28
path-walk.c
28
path-walk.c
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@ -12,6 +12,7 @@
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#include "object.h"
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#include "oid-array.h"
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#include "prio-queue.h"
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#include "repository.h"
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#include "revision.h"
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#include "string-list.h"
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#include "strmap.h"
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@ -172,6 +173,23 @@ static int add_tree_entries(struct path_walk_context *ctx,
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if (type == OBJ_TREE)
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strbuf_addch(&path, '/');
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if (ctx->info->pl) {
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int dtype;
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enum pattern_match_result match;
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match = path_matches_pattern_list(path.buf, path.len,
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path.buf + base_len, &dtype,
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ctx->info->pl,
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ctx->repo->index);
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if (ctx->info->pl->use_cone_patterns &&
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match == NOT_MATCHED)
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continue;
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else if (!ctx->info->pl->use_cone_patterns &&
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type == OBJ_BLOB &&
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match != MATCHED)
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continue;
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}
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if (!(list = strmap_get(&ctx->paths_to_lists, path.buf))) {
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CALLOC_ARRAY(list, 1);
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list->type = type;
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@ -582,10 +600,10 @@ void path_walk_info_init(struct path_walk_info *info)
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memcpy(info, &empty, sizeof(empty));
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}
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void path_walk_info_clear(struct path_walk_info *info UNUSED)
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void path_walk_info_clear(struct path_walk_info *info)
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{
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/*
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* This destructor is empty for now, as info->revs
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* is not owned by 'struct path_walk_info'.
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*/
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if (info->pl) {
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clear_pattern_list(info->pl);
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free(info->pl);
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}
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}
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11
path-walk.h
11
path-walk.h
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@ -6,6 +6,7 @@
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struct rev_info;
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struct oid_array;
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struct pattern_list;
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/**
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* The type of a function pointer for the method that is called on a list of
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@ -48,6 +49,16 @@ struct path_walk_info {
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* walk the children of such trees.
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*/
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int prune_all_uninteresting;
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/**
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* Specify a sparse-checkout definition to match our paths to. Do not
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* walk outside of this sparse definition. If the patterns are in
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* cone mode, then the search may prune directories that are outside
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* of the cone. If not in cone mode, then all tree paths will be
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* explored but the path_fn will only be called when the path matches
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* the sparse-checkout patterns.
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*/
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struct pattern_list *pl;
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};
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#define PATH_WALK_INFO_INIT { \
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@ -1,6 +1,7 @@
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#define USE_THE_REPOSITORY_VARIABLE
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#include "test-tool.h"
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#include "dir.h"
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#include "environment.h"
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#include "hex.h"
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#include "object-name.h"
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@ -9,6 +10,7 @@
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#include "revision.h"
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#include "setup.h"
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#include "parse-options.h"
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#include "strbuf.h"
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#include "path-walk.h"
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#include "oid-array.h"
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@ -65,7 +67,7 @@ static int emit_block(const char *path, struct oid_array *oids,
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int cmd__path_walk(int argc, const char **argv)
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{
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int res;
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int res, stdin_pl = 0;
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struct rev_info revs = REV_INFO_INIT;
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struct path_walk_info info = PATH_WALK_INFO_INIT;
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struct path_walk_test_data data = { 0 };
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@ -80,6 +82,8 @@ int cmd__path_walk(int argc, const char **argv)
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N_("toggle inclusion of tree objects")),
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OPT_BOOL(0, "prune", &info.prune_all_uninteresting,
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N_("toggle pruning of uninteresting paths")),
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OPT_BOOL(0, "stdin-pl", &stdin_pl,
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N_("read a pattern list over stdin")),
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OPT_END(),
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};
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@ -99,6 +103,17 @@ int cmd__path_walk(int argc, const char **argv)
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info.path_fn = emit_block;
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info.path_fn_data = &data;
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if (stdin_pl) {
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struct strbuf in = STRBUF_INIT;
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CALLOC_ARRAY(info.pl, 1);
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info.pl->use_cone_patterns = 1;
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strbuf_fread(&in, 2048, stdin);
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add_patterns_from_buffer(in.buf, in.len, "", 0, info.pl);
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strbuf_release(&in);
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}
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res = walk_objects_by_path(&info);
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printf("commits:%" PRIuMAX "\n"
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@ -107,6 +122,11 @@ int cmd__path_walk(int argc, const char **argv)
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"tags:%" PRIuMAX "\n",
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data.commit_nr, data.tree_nr, data.blob_nr, data.tag_nr);
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if (info.pl) {
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clear_pattern_list(info.pl);
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free(info.pl);
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}
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release_revisions(&revs);
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return res;
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}
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@ -77,6 +77,94 @@ test_expect_success 'do partial clone 2, backfill min batch size' '
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test_line_count = 0 revs2
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'
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test_expect_success 'backfill --sparse' '
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git clone --sparse --filter=blob:none \
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--single-branch --branch=main \
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"file://$(pwd)/srv.bare" backfill3 &&
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# Initial checkout includes four files at root.
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git -C backfill3 rev-list --quiet --objects --missing=print HEAD >missing &&
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test_line_count = 44 missing &&
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# Initial sparse-checkout is just the files at root, so we get the
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# older versions of the four files at tip.
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GIT_TRACE2_EVENT="$(pwd)/sparse-trace1" git \
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-C backfill3 backfill --sparse &&
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test_trace2_data promisor fetch_count 4 <sparse-trace1 &&
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test_trace2_data path-walk paths 5 <sparse-trace1 &&
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git -C backfill3 rev-list --quiet --objects --missing=print HEAD >missing &&
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test_line_count = 40 missing &&
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# Expand the sparse-checkout to include 'd' recursively. This
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# engages the algorithm to skip the trees for 'a'. Note that
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# the "sparse-checkout set" command downloads the objects at tip
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# to satisfy the current checkout.
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git -C backfill3 sparse-checkout set d &&
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GIT_TRACE2_EVENT="$(pwd)/sparse-trace2" git \
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-C backfill3 backfill --sparse &&
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test_trace2_data promisor fetch_count 8 <sparse-trace2 &&
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test_trace2_data path-walk paths 15 <sparse-trace2 &&
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git -C backfill3 rev-list --quiet --objects --missing=print HEAD >missing &&
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test_line_count = 24 missing
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'
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test_expect_success 'backfill --sparse without cone mode (positive)' '
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git clone --no-checkout --filter=blob:none \
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--single-branch --branch=main \
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"file://$(pwd)/srv.bare" backfill4 &&
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# No blobs yet
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git -C backfill4 rev-list --quiet --objects --missing=print HEAD >missing &&
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test_line_count = 48 missing &&
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# Define sparse-checkout by filename regardless of parent directory.
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# This downloads 6 blobs to satisfy the checkout.
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git -C backfill4 sparse-checkout set --no-cone "**/file.1.txt" &&
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git -C backfill4 checkout main &&
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# Track new blob count
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git -C backfill4 rev-list --quiet --objects --missing=print HEAD >missing &&
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test_line_count = 42 missing &&
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GIT_TRACE2_EVENT="$(pwd)/no-cone-trace1" git \
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-C backfill4 backfill --sparse &&
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test_trace2_data promisor fetch_count 6 <no-cone-trace1 &&
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# This walk needed to visit all directories to search for these paths.
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test_trace2_data path-walk paths 12 <no-cone-trace1 &&
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git -C backfill4 rev-list --quiet --objects --missing=print HEAD >missing &&
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test_line_count = 36 missing
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'
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test_expect_success 'backfill --sparse without cone mode (negative)' '
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git clone --no-checkout --filter=blob:none \
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--single-branch --branch=main \
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"file://$(pwd)/srv.bare" backfill5 &&
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# No blobs yet
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git -C backfill5 rev-list --quiet --objects --missing=print HEAD >missing &&
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test_line_count = 48 missing &&
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# Define sparse-checkout by filename regardless of parent directory.
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# This downloads 18 blobs to satisfy the checkout
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git -C backfill5 sparse-checkout set --no-cone "**/file*" "!**/file.1.txt" &&
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git -C backfill5 checkout main &&
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# Track new blob count
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git -C backfill5 rev-list --quiet --objects --missing=print HEAD >missing &&
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test_line_count = 30 missing &&
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GIT_TRACE2_EVENT="$(pwd)/no-cone-trace2" git \
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-C backfill5 backfill --sparse &&
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test_trace2_data promisor fetch_count 18 <no-cone-trace2 &&
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# This walk needed to visit all directories to search for these paths, plus
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# 12 extra "file.?.txt" paths than the previous test.
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test_trace2_data path-walk paths 24 <no-cone-trace2 &&
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git -C backfill5 rev-list --quiet --objects --missing=print HEAD >missing &&
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test_line_count = 12 missing
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'
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. "$TEST_DIRECTORY"/lib-httpd.sh
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start_httpd
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@ -176,6 +176,38 @@ test_expect_success 'branches and indexed objects mix well' '
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test_cmp_sorted expect out
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'
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test_expect_success 'base & topic, sparse' '
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cat >patterns <<-EOF &&
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/*
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!/*/
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/left/
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EOF
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test-tool path-walk --stdin-pl -- base topic <patterns >out &&
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cat >expect <<-EOF &&
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0:commit::$(git rev-parse topic)
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0:commit::$(git rev-parse base)
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0:commit::$(git rev-parse base~1)
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0:commit::$(git rev-parse base~2)
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1:tree::$(git rev-parse topic^{tree})
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1:tree::$(git rev-parse base^{tree})
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1:tree::$(git rev-parse base~1^{tree})
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1:tree::$(git rev-parse base~2^{tree})
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2:blob:a:$(git rev-parse base~2:a)
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3:tree:left/:$(git rev-parse base:left)
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3:tree:left/:$(git rev-parse base~2:left)
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4:blob:left/b:$(git rev-parse base~2:left/b)
|
||||
4:blob:left/b:$(git rev-parse base:left/b)
|
||||
blobs:3
|
||||
commits:4
|
||||
tags:0
|
||||
trees:6
|
||||
EOF
|
||||
|
||||
test_cmp_sorted expect out
|
||||
'
|
||||
|
||||
test_expect_success 'topic only' '
|
||||
test-tool path-walk -- topic >out &&
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue