thodg/libgit2/examples/merge.c

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• Hash : 2ba7dbbe
  Author :
  Date : 2019-06-24T14:55:15
  

  Resolve static check warnings in example code Using cppcheck on libgit2 sources indicated two warnings in example code. merge.c was reported as having a memory leak. Fix applied was to `free()` memory pointed to by `parents`. init.c was reported as having a null pointer dereference on variable arg. Function 'usage' was being called with a null variable. Changed supplied parameter to empty string.

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• examples/merge.c

• /*
   * libgit2 "merge" example - shows how to perform merges
   *
   * 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/>.
   */
  
  #include "common.h"
  #include <assert.h>
  
  /** The following example demonstrates how to do merges with libgit2.
   *
   * It will merge whatever commit-ish you pass in into the current branch.
   *
   * Recognized options are :
   *  --no-commit: don't actually commit the merge.
   *
   */
  
  typedef struct {
  	const char **heads;
  	size_t heads_count;
  
  	git_annotated_commit **annotated;
  	size_t annotated_count;
  
  	int no_commit : 1;
  } merge_options;
  
  static void print_usage(void)
  {
  	fprintf(stderr, "usage: merge [--no-commit] <commit...>\n");
  	exit(1);
  }
  
  static void merge_options_init(merge_options *opts)
  {
  	memset(opts, 0, sizeof(*opts));
  
  	opts->heads = NULL;
  	opts->heads_count = 0;
  	opts->annotated = NULL;
  	opts->annotated_count = 0;
  }
  
  static void opts_add_refish(merge_options *opts, const char *refish)
  {
  	size_t sz;
  
  	assert(opts != NULL);
  
  	sz = ++opts->heads_count * sizeof(opts->heads[0]);
  	opts->heads = xrealloc(opts->heads, sz);
  	opts->heads[opts->heads_count - 1] = refish;
  }
  
  static void parse_options(const char **repo_path, merge_options *opts, int argc, char **argv)
  {
  	struct args_info args = ARGS_INFO_INIT;
  
  	if (argc <= 1)
  		print_usage();
  
  	for (args.pos = 1; args.pos < argc; ++args.pos) {
  		const char *curr = argv[args.pos];
  
  		if (curr[0] != '-') {
  			opts_add_refish(opts, curr);
  		} else if (!strcmp(curr, "--no-commit")) {
  			opts->no_commit = 1;
  		} else if (match_str_arg(repo_path, &args, "--git-dir")) {
  			continue;
  		} else {
  			print_usage();
  		}
  	}
  }
  
  static int resolve_heads(git_repository *repo, merge_options *opts)
  {
  	git_annotated_commit **annotated = calloc(opts->heads_count, sizeof(git_annotated_commit *));
  	size_t annotated_count = 0, i;
  	int err = 0;
  
  	for (i = 0; i < opts->heads_count; i++) {
  		err = resolve_refish(&annotated[annotated_count++], repo, opts->heads[i]);
  		if (err != 0) {
  			fprintf(stderr, "failed to resolve refish %s: %s\n", opts->heads[i], git_error_last()->message);
  			annotated_count--;
  			continue;
  		}
  	}
  
  	if (annotated_count != opts->heads_count) {
  		fprintf(stderr, "unable to parse some refish\n");
  		free(annotated);
  		return -1;
  	}
  
  	opts->annotated = annotated;
  	opts->annotated_count = annotated_count;
  	return 0;
  }
  
  static int perform_fastforward(git_repository *repo, const git_oid *target_oid, int is_unborn)
  {
  	git_checkout_options ff_checkout_options = GIT_CHECKOUT_OPTIONS_INIT;
  	git_reference *target_ref;
  	git_reference *new_target_ref;
  	git_object *target = NULL;
  	int err = 0;
  
  	if (is_unborn) {
  		const char *symbolic_ref;
  		git_reference *head_ref;
  
  		/* HEAD reference is unborn, lookup manually so we don't try to resolve it */
  		err = git_reference_lookup(&head_ref, repo, "HEAD");
  		if (err != 0) {
  			fprintf(stderr, "failed to lookup HEAD ref\n");
  			return -1;
  		}
  
  		/* Grab the reference HEAD should be pointing to */
  		symbolic_ref = git_reference_symbolic_target(head_ref);
  
  		/* Create our master reference on the target OID */
  		err = git_reference_create(&target_ref, repo, symbolic_ref, target_oid, 0, NULL);
  		if (err != 0) {
  			fprintf(stderr, "failed to create master reference\n");
  			return -1;
  		}
  
  		git_reference_free(head_ref);
  	} else {
  		/* HEAD exists, just lookup and resolve */
  		err = git_repository_head(&target_ref, repo);
  		if (err != 0) {
  			fprintf(stderr, "failed to get HEAD reference\n");
  			return -1;
  		}
  	}
  
  	/* Lookup the target object */
  	err = git_object_lookup(&target, repo, target_oid, GIT_OBJECT_COMMIT);
  	if (err != 0) {
  		fprintf(stderr, "failed to lookup OID %s\n", git_oid_tostr_s(target_oid));
  		return -1;
  	}
  
  	/* Checkout the result so the workdir is in the expected state */
  	ff_checkout_options.checkout_strategy = GIT_CHECKOUT_SAFE;
  	err = git_checkout_tree(repo, target, &ff_checkout_options);
  	if (err != 0) {
  		fprintf(stderr, "failed to checkout HEAD reference\n");
  		return -1;
  	}
  
  	/* Move the target reference to the target OID */
  	err = git_reference_set_target(&new_target_ref, target_ref, target_oid, NULL);
  	if (err != 0) {
  		fprintf(stderr, "failed to move HEAD reference\n");
  		return -1;
  	}
  
  	git_reference_free(target_ref);
  	git_reference_free(new_target_ref);
  	git_object_free(target);
  
  	return 0;
  }
  
  static void output_conflicts(git_index *index)
  {
  	git_index_conflict_iterator *conflicts;
  	const git_index_entry *ancestor;
  	const git_index_entry *our;
  	const git_index_entry *their;
  	int err = 0;
  
  	check_lg2(git_index_conflict_iterator_new(&conflicts, index), "failed to create conflict iterator", NULL);
  
  	while ((err = git_index_conflict_next(&ancestor, &our, &their, conflicts)) == 0) {
  		fprintf(stderr, "conflict: a:%s o:%s t:%s\n",
  		        ancestor ? ancestor->path : "NULL",
  		        our->path ? our->path : "NULL",
  		        their->path ? their->path : "NULL");
  	}
  
  	if (err != GIT_ITEROVER) {
  		fprintf(stderr, "error iterating conflicts\n");
  	}
  
  	git_index_conflict_iterator_free(conflicts);
  }
  
  static int create_merge_commit(git_repository *repo, git_index *index, merge_options *opts)
  {
  	git_oid tree_oid, commit_oid;
  	git_tree *tree;
  	git_signature *sign;
  	git_reference *merge_ref = NULL;
  	git_annotated_commit *merge_commit;
  	git_reference *head_ref;
  	git_commit **parents = calloc(opts->annotated_count + 1, sizeof(git_commit *));
  	const char *msg_target = NULL;
  	size_t msglen = 0;
  	char *msg;
  	size_t i;
  	int err;
  
  	/* Grab our needed references */
  	check_lg2(git_repository_head(&head_ref, repo), "failed to get repo HEAD", NULL);
  	if (resolve_refish(&merge_commit, repo, opts->heads[0])) {
  		fprintf(stderr, "failed to resolve refish %s", opts->heads[0]);
  		free(parents);
  		return -1;
  	}
  
  	/* Maybe that's a ref, so DWIM it */
  	err = git_reference_dwim(&merge_ref, repo, opts->heads[0]);
  	check_lg2(err, "failed to DWIM reference", git_error_last()->message);
  
  	/* Grab a signature */
  	check_lg2(git_signature_now(&sign, "Me", "me@example.com"), "failed to create signature", NULL);
  
  #define MERGE_COMMIT_MSG "Merge %s '%s'"
  	/* Prepare a standard merge commit message */
  	if (merge_ref != NULL) {
  		check_lg2(git_branch_name(&msg_target, merge_ref), "failed to get branch name of merged ref", NULL);
  	} else {
  		msg_target = git_oid_tostr_s(git_annotated_commit_id(merge_commit));
  	}
  
  	msglen = snprintf(NULL, 0, MERGE_COMMIT_MSG, (merge_ref ? "branch" : "commit"), msg_target);
  	if (msglen > 0) msglen++;
  	msg = malloc(msglen);
  	err = snprintf(msg, msglen, MERGE_COMMIT_MSG, (merge_ref ? "branch" : "commit"), msg_target);
  
  	/* This is only to silence the compiler */
  	if (err < 0) goto cleanup;
  
  	/* Setup our parent commits */
  	err = git_reference_peel((git_object **)&parents[0], head_ref, GIT_OBJECT_COMMIT);
  	check_lg2(err, "failed to peel head reference", NULL);
  	for (i = 0; i < opts->annotated_count; i++) {
  		git_commit_lookup(&parents[i + 1], repo, git_annotated_commit_id(opts->annotated[i]));
  	}
  
  	/* Prepare our commit tree */
  	check_lg2(git_index_write_tree(&tree_oid, index), "failed to write merged tree", NULL);
  	check_lg2(git_tree_lookup(&tree, repo, &tree_oid), "failed to lookup tree", NULL);
  
  	/* Commit time ! */
  	err = git_commit_create(&commit_oid,
  	                        repo, git_reference_name(head_ref),
  	                        sign, sign,
  	                        NULL, msg,
  	                        tree,
  	                        opts->annotated_count + 1, (const git_commit **)parents);
  	check_lg2(err, "failed to create commit", NULL);
  
  	/* We're done merging, cleanup the repository state */
  	git_repository_state_cleanup(repo);
  
  cleanup:
  	free(parents);
  	return err;
  }
  
  int lg2_merge(git_repository *repo, int argc, char **argv)
  {
  	merge_options opts;
  	git_index *index;
  	git_repository_state_t state;
  	git_merge_analysis_t analysis;
  	git_merge_preference_t preference;
  	const char *path = ".";
  	int err = 0;
  
  	merge_options_init(&opts);
  	parse_options(&path, &opts, argc, argv);
  
  	state = git_repository_state(repo);
  	if (state != GIT_REPOSITORY_STATE_NONE) {
  		fprintf(stderr, "repository is in unexpected state %d\n", state);
  		goto cleanup;
  	}
  
  	err = resolve_heads(repo, &opts);
  	if (err != 0)
  		goto cleanup;
  
  	err = git_merge_analysis(&analysis, &preference,
  	                         repo,
  	                         (const git_annotated_commit **)opts.annotated,
  	                         opts.annotated_count);
  	check_lg2(err, "merge analysis failed", NULL);
  
  	if (analysis & GIT_MERGE_ANALYSIS_UP_TO_DATE) {
  		printf("Already up-to-date\n");
  		return 0;
  	} else if (analysis & GIT_MERGE_ANALYSIS_UNBORN ||
  	          (analysis & GIT_MERGE_ANALYSIS_FASTFORWARD &&
  	          !(preference & GIT_MERGE_PREFERENCE_NO_FASTFORWARD))) {
  		const git_oid *target_oid;
  		if (analysis & GIT_MERGE_ANALYSIS_UNBORN) {
  			printf("Unborn\n");
  		} else {
  			printf("Fast-forward\n");
  		}
  
  		/* Since this is a fast-forward, there can be only one merge head */
  		target_oid = git_annotated_commit_id(opts.annotated[0]);
  		assert(opts.annotated_count == 1);
  
  		return perform_fastforward(repo, target_oid, (analysis & GIT_MERGE_ANALYSIS_UNBORN));
  	} else if (analysis & GIT_MERGE_ANALYSIS_NORMAL) {
  		git_merge_options merge_opts = GIT_MERGE_OPTIONS_INIT;
  		git_checkout_options checkout_opts = GIT_CHECKOUT_OPTIONS_INIT;
  
  		merge_opts.flags = 0;
  		merge_opts.file_flags = GIT_MERGE_FILE_STYLE_DIFF3;
  
  		checkout_opts.checkout_strategy = GIT_CHECKOUT_FORCE|GIT_CHECKOUT_ALLOW_CONFLICTS;
  
  		if (preference & GIT_MERGE_PREFERENCE_FASTFORWARD_ONLY) {
  			printf("Fast-forward is preferred, but only a merge is possible\n");
  			return -1;
  		}
  
  		err = git_merge(repo,
  		                (const git_annotated_commit **)opts.annotated, opts.annotated_count,
  		                &merge_opts, &checkout_opts);
  		check_lg2(err, "merge failed", NULL);
  	}
  
  	/* If we get here, we actually performed the merge above */
  
  	check_lg2(git_repository_index(&index, repo), "failed to get repository index", NULL);
  
  	if (git_index_has_conflicts(index)) {
  		/* Handle conflicts */
  		output_conflicts(index);
  	} else if (!opts.no_commit) {
  		create_merge_commit(repo, index, &opts);
  		printf("Merge made\n");
  	}
  
  cleanup:
  	free(opts.heads);
  	free(opts.annotated);
  
  	return 0;
  }
  

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