Merge pull request #4051 from tiennou/clang-analyzer-1

[libgit2.git] / examples / general.c

/*
 * 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
 */

/**
 * ### 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>
#include <stdio.h>
#include <string.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 = giterr_last();
        if (!error_code)
                return;

        printf("Error %d %s - %s\n", error_code, action,
                        (error && error->message) ? error->message : "???");

        exit(1);
}

int main (int argc, char** argv)
{
        int error;
        git_oid oid;
        char *repo_path;
        git_repository *repo;

        /**
         * 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_HEXSZ+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.
         */
        git_oid_fromstr(oid, hex);

        // 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_HEXSZ] = '\0';

        /**
         * If you have a oid, you can easily get the hex value of the SHA as well.
         */
        git_oid_fmt(out, oid);

        /**
         * 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_HEXSZ+1] = { 0 };
        const unsigned char *data;
        const char *str_type;
        int error;
        git_odb_object *obj;
        git_odb *odb;
        git_otype 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_OBJ_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_HEXSZ+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
         */
        git_oid_fromstr(&tree_id, "f60079018b664e4e79329a7ef9559c8d9e0378d1");
        git_tree_lookup(&tree, repo, &tree_id);
        git_oid_fromstr(&parent_id, "5b5b025afb0b4c913b4c338a42934a3863bf3644");
        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_HEXSZ+1];
        const char *message;
        unsigned int parents, p;
        int error;
        time_t time;

        printf("\n*Commit Parsing*\n");

        git_oid_fromstr(&oid, "8496071c1b46c854b31185ea97743be6a8774479");

        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_otype 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).
         */
        git_oid_fromstr(&oid, "b25fa35b38051e4ae45d4222e795f9df2e43f1d1");

        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_OBJ_COMMIT (otype 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.
         */
        git_oid_fromstr(&oid, "f60079018b664e4e79329a7ef9559c8d9e0378d1");
        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");

        git_oid_fromstr(&oid, "1385f264afb75a56a5bec74243be9b367ba4ca08");
        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");

        git_oid_fromstr(&oid, "5b5b025afb0b4c913b4c338a42934a3863bf3644");

        /**
         * 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;
        unsigned int 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_HEXSZ+1] = GIT_OID_HEX_ZERO;
                const char *refname;

                refname = ref_list.strings[i];
                git_reference_lookup(&ref, repo, refname);

                switch (git_reference_type(ref)) {
                        case GIT_REF_OID:
                                git_oid_fmt(oid_hex, git_reference_target(ref));
                                printf("%s [%s]\n", refname, oid_hex);
                                break;

                        case GIT_REF_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_free(&ref_list);
}

/**
 * ### Config Files
 *
 * The [config API][config] allows you to list and updatee 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;

        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);

        /**
         * Remember to free the configurations after usage.
         */
        git_config_free(cfg);
        git_config_free(snap_cfg);
}