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Diffstat (limited to 'Documentation/MyFirstObjectWalk.txt')
| -rw-r--r-- | Documentation/MyFirstObjectWalk.txt | 67 |
1 files changed, 43 insertions, 24 deletions
diff --git a/Documentation/MyFirstObjectWalk.txt b/Documentation/MyFirstObjectWalk.txt index 8d9e855..dec8afe 100644 --- a/Documentation/MyFirstObjectWalk.txt +++ b/Documentation/MyFirstObjectWalk.txt @@ -41,6 +41,7 @@ Open up a new file `builtin/walken.c` and set up the command handler: */ #include "builtin.h" +#include "trace.h" int cmd_walken(int argc, const char **argv, const char *prefix) { @@ -49,12 +50,13 @@ int cmd_walken(int argc, const char **argv, const char *prefix) } ---- -NOTE: `trace_printf()` differs from `printf()` in that it can be turned on or -off at runtime. For the purposes of this tutorial, we will write `walken` as -though it is intended for use as a "plumbing" command: that is, a command which -is used primarily in scripts, rather than interactively by humans (a "porcelain" -command). So we will send our debug output to `trace_printf()` instead. When -running, enable trace output by setting the environment variable `GIT_TRACE`. +NOTE: `trace_printf()`, defined in `trace.h`, differs from `printf()` in +that it can be turned on or off at runtime. For the purposes of this +tutorial, we will write `walken` as though it is intended for use as +a "plumbing" command: that is, a command which is used primarily in +scripts, rather than interactively by humans (a "porcelain" command). +So we will send our debug output to `trace_printf()` instead. +When running, enable trace output by setting the environment variable `GIT_TRACE`. Add usage text and `-h` handling, like all subcommands should consistently do (our test suite will notice and complain if you fail to do so). @@ -124,7 +126,7 @@ parameters provided by the user over the CLI. `nr` represents the number of `rev_cmdline_entry` present in the array. -`alloc` is used by the `ALLOC_GROW` macro. Check `cache.h` - this variable is +`alloc` is used by the `ALLOC_GROW` macro. Check `alloc.h` - this variable is used to track the allocated size of the list. Per entry, we find: @@ -208,13 +210,14 @@ We'll also need to include the `config.h` header: ... -static int git_walken_config(const char *var, const char *value, void *cb) +static int git_walken_config(const char *var, const char *value, + const struct config_context *ctx, void *cb) { /* * For now, we don't have any custom configuration, so fall back to * the default config. */ - return git_default_config(var, value, cb); + return git_default_config(var, value, ctx, cb); } ---- @@ -341,6 +344,10 @@ the walk loop below the `prepare_revision_walk()` call within your `walken_commit_walk()`: ---- +#include "pretty.h" + +... + static void walken_commit_walk(struct rev_info *rev) { struct commit *commit; @@ -383,10 +390,11 @@ modifying `rev_info.grep_filter`, which is a `struct grep_opt`. First some setup. Add `grep_config()` to `git_walken_config()`: ---- -static int git_walken_config(const char *var, const char *value, void *cb) +static int git_walken_config(const char *var, const char *value, + const struct config_context *ctx, void *cb) { - grep_config(var, value, cb); - return git_default_config(var, value, cb); + grep_config(var, value, ctx, cb); + return git_default_config(var, value, ctx, cb); } ---- @@ -517,7 +525,7 @@ about each one. We can base our work on an example. `git pack-objects` prepares all kinds of objects for packing into a bitmap or packfile. The work we are interested in -resides in `builtins/pack-objects.c:get_object_list()`; examination of that +resides in `builtin/pack-objects.c:get_object_list()`; examination of that function shows that the all-object walk is being performed by `traverse_commit_list()` or `traverse_commit_list_filtered()`. Those two functions reside in `list-objects.c`; examining the source shows that, despite @@ -534,7 +542,7 @@ the arguments to `traverse_commit_list()`. - `void *show_data`: A context buffer which is passed in turn to `show_commit` and `show_object`. -In addition, `traverse_commit_list_filtered()` has an additional paramter: +In addition, `traverse_commit_list_filtered()` has an additional parameter: - `struct oidset *omitted`: A linked-list of object IDs which the provided filter caused to be omitted. @@ -726,8 +734,8 @@ walk we've just performed: } else { trace_printf( _("Filtered object walk with filterspec 'tree:1'.\n")); - CALLOC_ARRAY(rev->filter, 1); - parse_list_objects_filter(rev->filter, "tree:1"); + + parse_list_objects_filter(&rev->filter, "tree:1"); } traverse_commit_list(rev, walken_show_commit, walken_show_object, NULL); @@ -746,14 +754,20 @@ points to the same tree object as its grandparent.) === Counting Omitted Objects We also have the capability to enumerate all objects which were omitted by a -filter, like with `git log --filter=<spec> --filter-print-omitted`. Asking -`traverse_commit_list_filtered()` to populate the `omitted` list means that our -object walk does not perform any better than an unfiltered object walk; all -reachable objects are walked in order to populate the list. +filter, like with `git log --filter=<spec> --filter-print-omitted`. To do this, +change `traverse_commit_list()` to `traverse_commit_list_filtered()`, which is +able to populate an `omitted` list. Asking for this list of filtered objects +may cause performance degradations, however, because in this case, despite +filtering objects, the possibly much larger set of all reachable objects must +be processed in order to populate that list. First, add the `struct oidset` and related items we will use to iterate it: ---- +#include "oidset.h" + +... + static void walken_object_walk( ... @@ -766,8 +780,9 @@ static void walken_object_walk( ... ---- -Modify the call to `traverse_commit_list_filtered()` to include your `omitted` -object: +Replace the call to `traverse_commit_list()` with +`traverse_commit_list_filtered()` and pass a pointer to the `omitted` oidset +defined and initialized above: ---- ... @@ -805,6 +820,10 @@ just walks of commits. First, we'll make our handlers chattier - modify go: ---- +#include "hex.h" + +... + static void walken_show_commit(struct commit *cmt, void *buf) { trace_printf("commit: %s\n", oid_to_hex(&cmt->object.oid)); @@ -829,7 +848,7 @@ those lines without having to recompile. With only that change, run again (but save yourself some scrollback): ---- -$ GIT_TRACE=1 ./bin-wrappers/git walken | head -n 10 +$ GIT_TRACE=1 ./bin-wrappers/git walken 2>&1 | head -n 10 ---- Take a look at the top commit with `git show` and the object ID you printed; it @@ -857,7 +876,7 @@ of the first handful: ---- $ make -$ GIT_TRACE=1 ./bin-wrappers git walken | tail -n 10 +$ GIT_TRACE=1 ./bin-wrappers/git walken 2>&1 | tail -n 10 ---- The last commit object given should have the same OID as the one we saw at the |