email: introduce git_email_create_from_commit

Create `git_email_*` which will encapsulate email creation and
application, and `git_email_create_from_commit` in particular, which
creates an email for a single commit.

Author: ethomson

include/git2.h

@@ -26,6 +26,7 @@
 #include "git2/deprecated.h"
 #include "git2/describe.h"
 #include "git2/diff.h"
+#include "git2/email.h"
 #include "git2/errors.h"
 #include "git2/filter.h"
 #include "git2/global.h"

include/git2/email.h

@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_git_email_h__
+#define INCLUDE_git_email_h__
+
+#include "common.h"
+
+/**
+ * @file git2/email.h
+ * @brief Git email formatting and application routines.
+ * @ingroup Git
+ * @{
+ */
+GIT_BEGIN_DECL
+
+/**
+ * Formatting options for diff e-mail generation
+ */
+typedef enum {
+	/** Normal patch, the default */
+	GIT_EMAIL_CREATE_DEFAULT = 0,
+
+	/** Do not include patch numbers in the subject prefix. */
+	GIT_EMAIL_CREATE_OMIT_NUMBERS = (1u << 0),
+
+	/**
+	 * Include numbers in the subject prefix even when the
+	 * patch is for a single commit (1/1).
+	 */
+	GIT_EMAIL_CREATE_ALWAYS_NUMBER = (1u << 1),
+} git_email_create_flags_t;
+
+/**
+ * Options for controlling the formatting of the generated e-mail.
+ */
+typedef struct {
+	unsigned int version;
+
+	/** see `git_email_create_flags_t` above */
+	uint32_t flags;
+
+	/** Options to use when creating diffs */
+	git_diff_options diff_opts;
+
+	/**
+	 * The subject prefix, by default "PATCH".  If set to an empty
+	 * string ("") then only the patch numbers will be shown in the
+	 * prefix.  If the subject_prefix is empty and patch numbers
+	 * are not being shown, the prefix will be omitted entirely.
+	 */
+	const char *subject_prefix;
+
+	/**
+	 * The starting patch number; this cannot be 0.  By default,
+	 * this is 1.
+	 */
+	size_t start_number;
+
+	/** The "re-roll" number.  By default, there is no re-roll. */
+	size_t reroll_number;
+} git_email_create_options;
+
+#define GIT_EMAIL_CREATE_OPTIONS_VERSION 1
+#define GIT_EMAIL_CREATE_OPTIONS_INIT { \
+		GIT_EMAIL_CREATE_OPTIONS_VERSION, \
+		GIT_EMAIL_CREATE_DEFAULT, \
+		GIT_DIFF_OPTIONS_INIT \
+	}
+
+/**
+ * Create a diff for a commit in mbox format for sending via email.
+ * The commit must not be a merge commit.
+ *
+ * @param out buffer to store the e-mail patch in
+ * @param commit commit to create a patch for
+ * @param opts email creation options
+ */
+GIT_EXTERN(int) git_email_create_from_commit(
+	git_buf *out,
+	git_commit *commit,
+	const git_email_create_options *opts);
+
+/**
+ * Create an mbox format diff for the given commits in the revision
+ * spec, excluding merge commits.
+ *
+ * @param out buffer to store the e-mail patches in
+ * @param commits the array of commits to create patches for
+ * @param len the length of the `commits` array
+ * @param opts email creation options
+ */
+GIT_EXTERN(int) git_email_create_from_commits(
+	git_strarray *out,
+	git_commit **commits,
+	size_t len,
+	const git_email_create_options *opts);
+
+GIT_END_DECL
+
+/** @} */
+
+#endif

src/email.c

@@ -0,0 +1,211 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "buffer.h"
+#include "common.h"
+#include "diff_generate.h"
+
+#include "git2/email.h"
+#include "git2/patch.h"
+#include "git2/version.h"
+
+/*
+ * Git uses a "magic" timestamp to indicate that an email message
+ * is from `git format-patch` (or our equivalent).
+ */
+#define EMAIL_TIMESTAMP "Mon Sep 17 00:00:00 2001"
+
+GIT_INLINE(int) include_prefix(
+	size_t patch_count,
+	git_email_create_options *opts)
+{
+	return ((!opts->subject_prefix || *opts->subject_prefix) ||
+	        (opts->flags & GIT_EMAIL_CREATE_ALWAYS_NUMBER) != 0 ||
+	        opts->reroll_number ||
+		(patch_count > 1 && !(opts->flags & GIT_EMAIL_CREATE_OMIT_NUMBERS)));
+}
+
+static int append_prefix(
+	git_buf *out,
+	size_t patch_idx,
+	size_t patch_count,
+	git_email_create_options *opts)
+{
+	const char *subject_prefix = opts->subject_prefix ?
+		opts->subject_prefix : "PATCH";
+
+	if (!include_prefix(patch_count, opts))
+		return 0;
+
+	git_buf_putc(out, '[');
+
+	if (*subject_prefix)
+		git_buf_puts(out, subject_prefix);
+
+	if (opts->reroll_number) {
+		if (*subject_prefix)
+			git_buf_putc(out, ' ');
+
+		git_buf_printf(out, "v%" PRIuZ, opts->reroll_number);
+	}
+
+	if ((opts->flags & GIT_EMAIL_CREATE_ALWAYS_NUMBER) != 0 ||
+	    (patch_count > 1 && !(opts->flags & GIT_EMAIL_CREATE_OMIT_NUMBERS))) {
+		size_t start_number = opts->start_number ?
+			opts->start_number : 1;
+
+		if (*subject_prefix || opts->reroll_number)
+			git_buf_putc(out, ' ');
+
+		git_buf_printf(out, "%" PRIuZ "/%" PRIuZ,
+		               patch_idx + (start_number - 1),
+		               patch_count + (start_number - 1));
+	}
+
+	git_buf_puts(out, "] ");
+
+	return git_buf_oom(out) ? -1 : 0;
+}
+
+static int append_subject(
+	git_buf *out,
+	git_commit *commit,
+	size_t patch_idx,
+	size_t patch_count,
+	git_email_create_options *opts)
+{
+	int error;
+
+	if ((error = git_buf_puts(out, "Subject: ")) < 0 ||
+	    (error = append_prefix(out, patch_idx, patch_count, opts)) < 0 ||
+	    (error = git_buf_puts(out, git_commit_summary(commit))) < 0 ||
+	    (error = git_buf_putc(out, '\n')) < 0)
+		return error;
+
+	return 0;
+}
+
+static int append_header(
+	git_buf *out,
+	git_commit *commit,
+	size_t patch_idx,
+	size_t patch_count,
+	git_email_create_options *opts)
+{
+	const git_signature *author = git_commit_author(commit);
+	char id[GIT_OID_HEXSZ];
+	char date[GIT_DATE_RFC2822_SZ];
+	int error;
+
+	if ((error = git_oid_fmt(id, git_commit_id(commit))) < 0 ||
+	    (error = git_buf_printf(out, "From %.*s %s\n", GIT_OID_HEXSZ, id, EMAIL_TIMESTAMP)) < 0 ||
+	    (error = git_buf_printf(out, "From: %s <%s>\n", author->name, author->email)) < 0 ||
+	    (error = git__date_rfc2822_fmt(date, sizeof(date), &author->when)) < 0 ||
+	    (error = git_buf_printf(out, "Date: %s\n", date)) < 0 ||
+	    (error = append_subject(out, commit, patch_idx, patch_count, opts)) < 0)
+		return error;
+
+	if ((error = git_buf_putc(out, '\n')) < 0)
+		return error;
+
+	return 0;
+}
+
+static int append_body(git_buf *out, git_commit *commit)
+{
+	const char *body = git_commit_body(commit);
+	size_t body_len;
+	int error;
+
+	if (!body)
+		return 0;
+
+	body_len = strlen(body);
+
+	if ((error = git_buf_puts(out, body)) < 0)
+		return error;
+
+	if (body_len && body[body_len - 1] != '\n')
+		error = git_buf_putc(out, '\n');
+
+	return error;
+}
+
+static int append_diffstat(git_buf *out, git_diff *diff)
+{
+	git_diff_stats *stats = NULL;
+	unsigned int format_flags;
+	int error;
+
+	format_flags = GIT_DIFF_STATS_FULL | GIT_DIFF_STATS_INCLUDE_SUMMARY;
+
+	if ((error = git_diff_get_stats(&stats, diff)) == 0 &&
+	    (error = git_diff_stats_to_buf(out, stats, format_flags, 0)) == 0)
+		error = git_buf_putc(out, '\n');
+
+	git_diff_stats_free(stats);
+	return error;
+}
+
+static int append_patches(git_buf *out, git_diff *diff)
+{
+	size_t i, deltas;
+	int error = 0;
+
+	deltas = git_diff_num_deltas(diff);
+
+	for (i = 0; i < deltas; ++i) {
+		git_patch *patch = NULL;
+
+		if ((error = git_patch_from_diff(&patch, diff, i)) >= 0)
+			error = git_patch_to_buf(out, patch);
+
+		git_patch_free(patch);
+
+		if (error < 0)
+			break;
+	}
+
+	return error;
+}
+
+int git_email_create_from_commit(
+	git_buf *out,
+	git_commit *commit,
+	const git_email_create_options *given_opts)
+{
+	git_diff *diff = NULL;
+	git_email_create_options opts = GIT_EMAIL_CREATE_OPTIONS_INIT;
+	git_repository *repo;
+	int error = 0;
+
+	GIT_ASSERT_ARG(out);
+	GIT_ASSERT_ARG(commit);
+
+	GIT_ERROR_CHECK_VERSION(given_opts,
+		GIT_EMAIL_CREATE_OPTIONS_VERSION,
+		"git_email_create_options");
+
+	if (given_opts)
+		memcpy(&opts, given_opts, sizeof(git_email_create_options));
+
+	git_buf_sanitize(out);
+	git_buf_clear(out);
+
+	repo = git_commit_owner(commit);
+
+	if ((error = git_diff__commit(&diff, repo, commit, &opts.diff_opts)) == 0 &&
+	    (error = append_header(out, commit, 1, 1, &opts)) == 0 &&
+	    (error = append_body(out, commit)) == 0 &&
+	    (error = git_buf_puts(out, "---\n")) == 0 &&
+	    (error = append_diffstat(out, diff)) == 0 &&
+	    (error = append_patches(out, diff)) == 0)
+		error = git_buf_puts(out, "--\nlibgit2 " LIBGIT2_VERSION "\n\n");
+
+	git_diff_free(diff);
+	return error;
+}