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diff --git a/examples/general.c b/examples/general.c new file mode 100644 index 0000000..7f44cd7 --- /dev/null +++ b/examples/general.c @@ -0,0 +1,798 @@ +/* + * libgit2 "general" example - shows basic libgit2 concepts + * + * Written by the libgit2 contributors + * + * To the extent possible under law, the author(s) have dedicated all copyright + * and related and neighboring rights to this software to the public domain + * worldwide. This software is distributed without any warranty. + * + * You should have received a copy of the CC0 Public Domain Dedication along + * with this software. If not, see + * <http://creativecommons.org/publicdomain/zero/1.0/>. + */ + +/** + * [**libgit2**][lg] is a portable, pure C implementation of the Git core + * methods provided as a re-entrant linkable library with a solid API, + * allowing you to write native speed custom Git applications in any + * language which supports C bindings. + * + * This file is an example of using that API in a real, compilable C file. + * As the API is updated, this file will be updated to demonstrate the new + * functionality. + * + * If you're trying to write something in C using [libgit2][lg], you should + * also check out the generated [API documentation][ap]. We try to link to + * the relevant sections of the API docs in each section in this file. + * + * **libgit2** (for the most part) only implements the core plumbing + * functions, not really the higher level porcelain stuff. For a primer on + * Git Internals that you will need to know to work with Git at this level, + * check out [Chapter 10][pg] of the Pro Git book. + * + * [lg]: http://libgit2.github.com + * [ap]: http://libgit2.github.com/libgit2 + * [pg]: https://git-scm.com/book/en/v2/Git-Internals-Plumbing-and-Porcelain + */ + +#include "common.h" + +/** + * ### Includes + * + * Including the `git2.h` header will include all the other libgit2 headers + * that you need. It should be the only thing you need to include in order + * to compile properly and get all the libgit2 API. + */ +#include "git2.h" + +static void oid_parsing(git_oid *out); +static void object_database(git_repository *repo, git_oid *oid); +static void commit_writing(git_repository *repo); +static void commit_parsing(git_repository *repo); +static void tag_parsing(git_repository *repo); +static void tree_parsing(git_repository *repo); +static void blob_parsing(git_repository *repo); +static void revwalking(git_repository *repo); +static void index_walking(git_repository *repo); +static void reference_listing(git_repository *repo); +static void config_files(const char *repo_path, git_repository *repo); + +/** + * Almost all libgit2 functions return 0 on success or negative on error. + * This is not production quality error checking, but should be sufficient + * as an example. + */ +static void check_error(int error_code, const char *action) +{ + const git_error *error = git_error_last(); + if (!error_code) + return; + + printf("Error %d %s - %s\n", error_code, action, + (error && error->message) ? error->message : "???"); + + exit(1); +} + +int lg2_general(git_repository *repo, int argc, char** argv) +{ + int error; + git_oid oid; + char *repo_path; + + /** + * Initialize the library, this will set up any global state which libgit2 needs + * including threading and crypto + */ + git_libgit2_init(); + + /** + * ### Opening the Repository + * + * There are a couple of methods for opening a repository, this being the + * simplest. There are also [methods][me] for specifying the index file + * and work tree locations, here we assume they are in the normal places. + * + * (Try running this program against tests/resources/testrepo.git.) + * + * [me]: http://libgit2.github.com/libgit2/#HEAD/group/repository + */ + repo_path = (argc > 1) ? argv[1] : "/opt/libgit2-test/.git"; + + error = git_repository_open(&repo, repo_path); + check_error(error, "opening repository"); + + oid_parsing(&oid); + object_database(repo, &oid); + commit_writing(repo); + commit_parsing(repo); + tag_parsing(repo); + tree_parsing(repo); + blob_parsing(repo); + revwalking(repo); + index_walking(repo); + reference_listing(repo); + config_files(repo_path, repo); + + /** + * Finally, when you're done with the repository, you can free it as well. + */ + git_repository_free(repo); + + return 0; +} + +/** + * ### SHA-1 Value Conversions + */ +static void oid_parsing(git_oid *oid) +{ + char out[GIT_OID_SHA1_HEXSIZE+1]; + char hex[] = "4a202b346bb0fb0db7eff3cffeb3c70babbd2045"; + + printf("*Hex to Raw*\n"); + + /** + * For our first example, we will convert a 40 character hex value to the + * 20 byte raw SHA1 value. + * + * The `git_oid` is the structure that keeps the SHA value. We will use + * this throughout the example for storing the value of the current SHA + * key we're working with. + */ +#ifdef GIT_EXPERIMENTAL_SHA256 + git_oid_fromstr(oid, hex, GIT_OID_SHA1); +#else + git_oid_fromstr(oid, hex); +#endif + + /* + * Once we've converted the string into the oid value, we can get the raw + * value of the SHA by accessing `oid.id` + * + * Next we will convert the 20 byte raw SHA1 value to a human readable 40 + * char hex value. + */ + printf("\n*Raw to Hex*\n"); + out[GIT_OID_SHA1_HEXSIZE] = '\0'; + + /** + * If you have a oid, you can easily get the hex value of the SHA as well. + */ + git_oid_fmt(out, oid); + printf("SHA hex string: %s\n", out); +} + +/** + * ### Working with the Object Database + * + * **libgit2** provides [direct access][odb] to the object database. The + * object database is where the actual objects are stored in Git. For + * working with raw objects, we'll need to get this structure from the + * repository. + * + * [odb]: http://libgit2.github.com/libgit2/#HEAD/group/odb + */ +static void object_database(git_repository *repo, git_oid *oid) +{ + char oid_hex[GIT_OID_SHA1_HEXSIZE+1] = { 0 }; + const unsigned char *data; + const char *str_type; + int error; + git_odb_object *obj; + git_odb *odb; + git_object_t otype; + + git_repository_odb(&odb, repo); + + /** + * #### Raw Object Reading + */ + + printf("\n*Raw Object Read*\n"); + + /** + * We can read raw objects directly from the object database if we have + * the oid (SHA) of the object. This allows us to access objects without + * knowing their type and inspect the raw bytes unparsed. + */ + error = git_odb_read(&obj, odb, oid); + check_error(error, "finding object in repository"); + + /** + * A raw object only has three properties - the type (commit, blob, tree + * or tag), the size of the raw data and the raw, unparsed data itself. + * For a commit or tag, that raw data is human readable plain ASCII + * text. For a blob it is just file contents, so it could be text or + * binary data. For a tree it is a special binary format, so it's unlikely + * to be hugely helpful as a raw object. + */ + data = (const unsigned char *)git_odb_object_data(obj); + otype = git_odb_object_type(obj); + + /** + * We provide methods to convert from the object type which is an enum, to + * a string representation of that value (and vice-versa). + */ + str_type = git_object_type2string(otype); + printf("object length and type: %d, %s\nobject data: %s\n", + (int)git_odb_object_size(obj), + str_type, data); + + /** + * For proper memory management, close the object when you are done with + * it or it will leak memory. + */ + git_odb_object_free(obj); + + /** + * #### Raw Object Writing + */ + + printf("\n*Raw Object Write*\n"); + + /** + * You can also write raw object data to Git. This is pretty cool because + * it gives you direct access to the key/value properties of Git. Here + * we'll write a new blob object that just contains a simple string. + * Notice that we have to specify the object type as the `git_otype` enum. + */ + git_odb_write(oid, odb, "test data", sizeof("test data") - 1, GIT_OBJECT_BLOB); + + /** + * Now that we've written the object, we can check out what SHA1 was + * generated when the object was written to our database. + */ + git_oid_fmt(oid_hex, oid); + printf("Written Object: %s\n", oid_hex); + + /** + * Free the object database after usage. + */ + git_odb_free(odb); +} + +/** + * #### Writing Commits + * + * libgit2 provides a couple of methods to create commit objects easily as + * well. There are four different create signatures, we'll just show one + * of them here. You can read about the other ones in the [commit API + * docs][cd]. + * + * [cd]: http://libgit2.github.com/libgit2/#HEAD/group/commit + */ +static void commit_writing(git_repository *repo) +{ + git_oid tree_id, parent_id, commit_id; + git_tree *tree; + git_commit *parent; + git_signature *author, *committer; + char oid_hex[GIT_OID_SHA1_HEXSIZE+1] = { 0 }; + + printf("\n*Commit Writing*\n"); + + /** + * Creating signatures for an authoring identity and time is simple. You + * will need to do this to specify who created a commit and when. Default + * values for the name and email should be found in the `user.name` and + * `user.email` configuration options. See the `config` section of this + * example file to see how to access config values. + */ + git_signature_new(&author, + "Scott Chacon", "schacon@gmail.com", 123456789, 60); + git_signature_new(&committer, + "Scott A Chacon", "scott@github.com", 987654321, 90); + + /** + * Commit objects need a tree to point to and optionally one or more + * parents. Here we're creating oid objects to create the commit with, + * but you can also use + */ +#ifdef GIT_EXPERIMENTAL_SHA256 + git_oid_fromstr(&tree_id, "f60079018b664e4e79329a7ef9559c8d9e0378d1", GIT_OID_SHA1); + git_oid_fromstr(&parent_id, "5b5b025afb0b4c913b4c338a42934a3863bf3644", GIT_OID_SHA1); +#else + git_oid_fromstr(&tree_id, "f60079018b664e4e79329a7ef9559c8d9e0378d1"); + git_oid_fromstr(&parent_id, "5b5b025afb0b4c913b4c338a42934a3863bf3644"); +#endif + git_tree_lookup(&tree, repo, &tree_id); + git_commit_lookup(&parent, repo, &parent_id); + + /** + * Here we actually create the commit object with a single call with all + * the values we need to create the commit. The SHA key is written to the + * `commit_id` variable here. + */ + git_commit_create_v( + &commit_id, /* out id */ + repo, + NULL, /* do not update the HEAD */ + author, + committer, + NULL, /* use default message encoding */ + "example commit", + tree, + 1, parent); + + /** + * Now we can take a look at the commit SHA we've generated. + */ + git_oid_fmt(oid_hex, &commit_id); + printf("New Commit: %s\n", oid_hex); + + /** + * Free all objects used in the meanwhile. + */ + git_tree_free(tree); + git_commit_free(parent); + git_signature_free(author); + git_signature_free(committer); +} + +/** + * ### Object Parsing + * + * libgit2 has methods to parse every object type in Git so you don't have + * to work directly with the raw data. This is much faster and simpler + * than trying to deal with the raw data yourself. + */ + +/** + * #### Commit Parsing + * + * [Parsing commit objects][pco] is simple and gives you access to all the + * data in the commit - the author (name, email, datetime), committer + * (same), tree, message, encoding and parent(s). + * + * [pco]: http://libgit2.github.com/libgit2/#HEAD/group/commit + */ +static void commit_parsing(git_repository *repo) +{ + const git_signature *author, *cmtter; + git_commit *commit, *parent; + git_oid oid; + char oid_hex[GIT_OID_SHA1_HEXSIZE+1]; + const char *message; + unsigned int parents, p; + int error; + time_t time; + + printf("\n*Commit Parsing*\n"); + +#ifdef GIT_EXPERIMENTAL_SHA256 + git_oid_fromstr(&oid, "8496071c1b46c854b31185ea97743be6a8774479", GIT_OID_SHA1); +#else + git_oid_fromstr(&oid, "8496071c1b46c854b31185ea97743be6a8774479"); +#endif + + error = git_commit_lookup(&commit, repo, &oid); + check_error(error, "looking up commit"); + + /** + * Each of the properties of the commit object are accessible via methods, + * including commonly needed variations, such as `git_commit_time` which + * returns the author time and `git_commit_message` which gives you the + * commit message (as a NUL-terminated string). + */ + message = git_commit_message(commit); + author = git_commit_author(commit); + cmtter = git_commit_committer(commit); + time = git_commit_time(commit); + + /** + * The author and committer methods return [git_signature] structures, + * which give you name, email and `when`, which is a `git_time` structure, + * giving you a timestamp and timezone offset. + */ + printf("Author: %s (%s)\nCommitter: %s (%s)\nDate: %s\nMessage: %s\n", + author->name, author->email, + cmtter->name, cmtter->email, + ctime(&time), message); + + /** + * Commits can have zero or more parents. The first (root) commit will + * have no parents, most commits will have one (i.e. the commit it was + * based on) and merge commits will have two or more. Commits can + * technically have any number, though it's rare to have more than two. + */ + parents = git_commit_parentcount(commit); + for (p = 0;p < parents;p++) { + memset(oid_hex, 0, sizeof(oid_hex)); + + git_commit_parent(&parent, commit, p); + git_oid_fmt(oid_hex, git_commit_id(parent)); + printf("Parent: %s\n", oid_hex); + git_commit_free(parent); + } + + git_commit_free(commit); +} + +/** + * #### Tag Parsing + * + * You can parse and create tags with the [tag management API][tm], which + * functions very similarly to the commit lookup, parsing and creation + * methods, since the objects themselves are very similar. + * + * [tm]: http://libgit2.github.com/libgit2/#HEAD/group/tag + */ +static void tag_parsing(git_repository *repo) +{ + git_commit *commit; + git_object_t type; + git_tag *tag; + git_oid oid; + const char *name, *message; + int error; + + printf("\n*Tag Parsing*\n"); + + /** + * We create an oid for the tag object if we know the SHA and look it up + * the same way that we would a commit (or any other object). + */ +#ifdef GIT_EXPERIMENTAL_SHA256 + git_oid_fromstr(&oid, "b25fa35b38051e4ae45d4222e795f9df2e43f1d1", GIT_OID_SHA1); +#else + git_oid_fromstr(&oid, "b25fa35b38051e4ae45d4222e795f9df2e43f1d1"); +#endif + + error = git_tag_lookup(&tag, repo, &oid); + check_error(error, "looking up tag"); + + /** + * Now that we have the tag object, we can extract the information it + * generally contains: the target (usually a commit object), the type of + * the target object (usually 'commit'), the name ('v1.0'), the tagger (a + * git_signature - name, email, timestamp), and the tag message. + */ + git_tag_target((git_object **)&commit, tag); + name = git_tag_name(tag); /* "test" */ + type = git_tag_target_type(tag); /* GIT_OBJECT_COMMIT (object_t enum) */ + message = git_tag_message(tag); /* "tag message\n" */ + printf("Tag Name: %s\nTag Type: %s\nTag Message: %s\n", + name, git_object_type2string(type), message); + + /** + * Free both the commit and tag after usage. + */ + git_commit_free(commit); + git_tag_free(tag); +} + +/** + * #### Tree Parsing + * + * [Tree parsing][tp] is a bit different than the other objects, in that + * we have a subtype which is the tree entry. This is not an actual + * object type in Git, but a useful structure for parsing and traversing + * tree entries. + * + * [tp]: http://libgit2.github.com/libgit2/#HEAD/group/tree + */ +static void tree_parsing(git_repository *repo) +{ + const git_tree_entry *entry; + size_t cnt; + git_object *obj; + git_tree *tree; + git_oid oid; + + printf("\n*Tree Parsing*\n"); + + /** + * Create the oid and lookup the tree object just like the other objects. + */ +#ifdef GIT_EXPERIMENTAL_SHA256 + git_oid_fromstr(&oid, "f60079018b664e4e79329a7ef9559c8d9e0378d1", GIT_OID_SHA1); +#else + git_oid_fromstr(&oid, "f60079018b664e4e79329a7ef9559c8d9e0378d1"); +#endif + git_tree_lookup(&tree, repo, &oid); + + /** + * Getting the count of entries in the tree so you can iterate over them + * if you want to. + */ + cnt = git_tree_entrycount(tree); /* 2 */ + printf("tree entries: %d\n", (int) cnt); + + entry = git_tree_entry_byindex(tree, 0); + printf("Entry name: %s\n", git_tree_entry_name(entry)); /* "README" */ + + /** + * You can also access tree entries by name if you know the name of the + * entry you're looking for. + */ + entry = git_tree_entry_byname(tree, "README"); + git_tree_entry_name(entry); /* "README" */ + + /** + * Once you have the entry object, you can access the content or subtree + * (or commit, in the case of submodules) that it points to. You can also + * get the mode if you want. + */ + git_tree_entry_to_object(&obj, repo, entry); /* blob */ + + /** + * Remember to close the looked-up object and tree once you are done using it + */ + git_object_free(obj); + git_tree_free(tree); +} + +/** + * #### Blob Parsing + * + * The last object type is the simplest and requires the least parsing + * help. Blobs are just file contents and can contain anything, there is + * no structure to it. The main advantage to using the [simple blob + * api][ba] is that when you're creating blobs you don't have to calculate + * the size of the content. There is also a helper for reading a file + * from disk and writing it to the db and getting the oid back so you + * don't have to do all those steps yourself. + * + * [ba]: http://libgit2.github.com/libgit2/#HEAD/group/blob + */ +static void blob_parsing(git_repository *repo) +{ + git_blob *blob; + git_oid oid; + + printf("\n*Blob Parsing*\n"); + +#ifdef GIT_EXPERIMENTAL_SHA256 + git_oid_fromstr(&oid, "1385f264afb75a56a5bec74243be9b367ba4ca08", GIT_OID_SHA1); +#else + git_oid_fromstr(&oid, "1385f264afb75a56a5bec74243be9b367ba4ca08"); +#endif + git_blob_lookup(&blob, repo, &oid); + + /** + * You can access a buffer with the raw contents of the blob directly. + * Note that this buffer may not be contain ASCII data for certain blobs + * (e.g. binary files): do not consider the buffer a NULL-terminated + * string, and use the `git_blob_rawsize` attribute to find out its exact + * size in bytes + * */ + printf("Blob Size: %ld\n", (long)git_blob_rawsize(blob)); /* 8 */ + git_blob_rawcontent(blob); /* "content" */ + + /** + * Free the blob after usage. + */ + git_blob_free(blob); +} + +/** + * ### Revwalking + * + * The libgit2 [revision walking api][rw] provides methods to traverse the + * directed graph created by the parent pointers of the commit objects. + * Since all commits point back to the commit that came directly before + * them, you can walk this parentage as a graph and find all the commits + * that were ancestors of (reachable from) a given starting point. This + * can allow you to create `git log` type functionality. + * + * [rw]: http://libgit2.github.com/libgit2/#HEAD/group/revwalk + */ +static void revwalking(git_repository *repo) +{ + const git_signature *cauth; + const char *cmsg; + int error; + git_revwalk *walk; + git_commit *wcommit; + git_oid oid; + + printf("\n*Revwalking*\n"); + +#ifdef GIT_EXPERIMENTAL_SHA256 + git_oid_fromstr(&oid, "5b5b025afb0b4c913b4c338a42934a3863bf3644", GIT_OID_SHA1); +#else + git_oid_fromstr(&oid, "5b5b025afb0b4c913b4c338a42934a3863bf3644"); +#endif + + /** + * To use the revwalker, create a new walker, tell it how you want to sort + * the output and then push one or more starting points onto the walker. + * If you want to emulate the output of `git log` you would push the SHA + * of the commit that HEAD points to into the walker and then start + * traversing them. You can also 'hide' commits that you want to stop at + * or not see any of their ancestors. So if you want to emulate `git log + * branch1..branch2`, you would push the oid of `branch2` and hide the oid + * of `branch1`. + */ + git_revwalk_new(&walk, repo); + git_revwalk_sorting(walk, GIT_SORT_TOPOLOGICAL | GIT_SORT_REVERSE); + git_revwalk_push(walk, &oid); + + /** + * Now that we have the starting point pushed onto the walker, we start + * asking for ancestors. It will return them in the sorting order we asked + * for as commit oids. We can then lookup and parse the committed pointed + * at by the returned OID; note that this operation is specially fast + * since the raw contents of the commit object will be cached in memory + */ + while ((git_revwalk_next(&oid, walk)) == 0) { + error = git_commit_lookup(&wcommit, repo, &oid); + check_error(error, "looking up commit during revwalk"); + + cmsg = git_commit_message(wcommit); + cauth = git_commit_author(wcommit); + printf("%s (%s)\n", cmsg, cauth->email); + + git_commit_free(wcommit); + } + + /** + * Like the other objects, be sure to free the revwalker when you're done + * to prevent memory leaks. Also, make sure that the repository being + * walked it not deallocated while the walk is in progress, or it will + * result in undefined behavior + */ + git_revwalk_free(walk); +} + +/** + * ### Index File Manipulation * + * The [index file API][gi] allows you to read, traverse, update and write + * the Git index file (sometimes thought of as the staging area). + * + * [gi]: http://libgit2.github.com/libgit2/#HEAD/group/index + */ +static void index_walking(git_repository *repo) +{ + git_index *index; + size_t i, ecount; + + printf("\n*Index Walking*\n"); + + /** + * You can either open the index from the standard location in an open + * repository, as we're doing here, or you can open and manipulate any + * index file with `git_index_open_bare()`. The index for the repository + * will be located and loaded from disk. + */ + git_repository_index(&index, repo); + + /** + * For each entry in the index, you can get a bunch of information + * including the SHA (oid), path and mode which map to the tree objects + * that are written out. It also has filesystem properties to help + * determine what to inspect for changes (ctime, mtime, dev, ino, uid, + * gid, file_size and flags) All these properties are exported publicly in + * the `git_index_entry` struct + */ + ecount = git_index_entrycount(index); + for (i = 0; i < ecount; ++i) { + const git_index_entry *e = git_index_get_byindex(index, i); + + printf("path: %s\n", e->path); + printf("mtime: %d\n", (int)e->mtime.seconds); + printf("fs: %d\n", (int)e->file_size); + } + + git_index_free(index); +} + +/** + * ### References + * + * The [reference API][ref] allows you to list, resolve, create and update + * references such as branches, tags and remote references (everything in + * the .git/refs directory). + * + * [ref]: http://libgit2.github.com/libgit2/#HEAD/group/reference + */ +static void reference_listing(git_repository *repo) +{ + git_strarray ref_list; + unsigned i; + + printf("\n*Reference Listing*\n"); + + /** + * Here we will implement something like `git for-each-ref` simply listing + * out all available references and the object SHA they resolve to. + * + * Now that we have the list of reference names, we can lookup each ref + * one at a time and resolve them to the SHA, then print both values out. + */ + + git_reference_list(&ref_list, repo); + + for (i = 0; i < ref_list.count; ++i) { + git_reference *ref; + char oid_hex[GIT_OID_SHA1_HEXSIZE+1] = GIT_OID_SHA1_HEXZERO; + const char *refname; + + refname = ref_list.strings[i]; + git_reference_lookup(&ref, repo, refname); + + switch (git_reference_type(ref)) { + case GIT_REFERENCE_DIRECT: + git_oid_fmt(oid_hex, git_reference_target(ref)); + printf("%s [%s]\n", refname, oid_hex); + break; + + case GIT_REFERENCE_SYMBOLIC: + printf("%s => %s\n", refname, git_reference_symbolic_target(ref)); + break; + default: + fprintf(stderr, "Unexpected reference type\n"); + exit(1); + } + + git_reference_free(ref); + } + + git_strarray_dispose(&ref_list); +} + +/** + * ### Config Files + * + * The [config API][config] allows you to list and update config values + * in any of the accessible config file locations (system, global, local). + * + * [config]: http://libgit2.github.com/libgit2/#HEAD/group/config + */ +static void config_files(const char *repo_path, git_repository* repo) +{ + const char *email; + char config_path[256]; + int32_t autocorrect; + git_config *cfg; + git_config *snap_cfg; + int error_code; + + printf("\n*Config Listing*\n"); + + /** + * Open a config object so we can read global values from it. + */ + sprintf(config_path, "%s/config", repo_path); + check_error(git_config_open_ondisk(&cfg, config_path), "opening config"); + + if (git_config_get_int32(&autocorrect, cfg, "help.autocorrect") == 0) + printf("Autocorrect: %d\n", autocorrect); + + check_error(git_repository_config_snapshot(&snap_cfg, repo), "config snapshot"); + git_config_get_string(&email, snap_cfg, "user.email"); + printf("Email: %s\n", email); + + error_code = git_config_get_int32(&autocorrect, cfg, "help.autocorrect"); + switch (error_code) + { + case 0: + printf("Autocorrect: %d\n", autocorrect); + break; + case GIT_ENOTFOUND: + printf("Autocorrect: Undefined\n"); + break; + default: + check_error(error_code, "get_int32 failed"); + } + git_config_free(cfg); + + check_error(git_repository_config_snapshot(&snap_cfg, repo), "config snapshot"); + error_code = git_config_get_string(&email, snap_cfg, "user.email"); + switch (error_code) + { + case 0: + printf("Email: %s\n", email); + break; + case GIT_ENOTFOUND: + printf("Email: Undefined\n"); + break; + default: + check_error(error_code, "get_string failed"); + } + + git_config_free(snap_cfg); +} |