libgit2
diff --git a/include/git2.h b/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"

diff --git a/include/git2/deprecated.h b/include/git2/deprecated.h
@@ -294,6 +294,102 @@ typedef git_configmap git_cvar_map;
 
 /**@}*/
 
+/** @name Deprecated Diff Functions and Constants
+ *
+ * These functions and enumeration values are retained for backward
+ * compatibility.  The newer versions of these functions and values
+ * should be preferred in all new code.
+ *
+ * There is no plan to remove these backward compatibility values at
+ * this time.
+ */
+/**@{*/
+
+/**
+ * Formatting options for diff e-mail generation
+ */
+typedef enum {
+	/** Normal patch, the default */
+	GIT_DIFF_FORMAT_EMAIL_NONE = 0,
+
+	/** Don't insert "[PATCH]" in the subject header*/
+	GIT_DIFF_FORMAT_EMAIL_EXCLUDE_SUBJECT_PATCH_MARKER = (1 << 0),
+
+} git_diff_format_email_flags_t;
+
+/**
+ * Options for controlling the formatting of the generated e-mail.
+ */
+typedef struct {
+	unsigned int version;
+
+	/** see `git_diff_format_email_flags_t` above */
+	uint32_t flags;
+
+	/** This patch number */
+	size_t patch_no;
+
+	/** Total number of patches in this series */
+	size_t total_patches;
+
+	/** id to use for the commit */
+	const git_oid *id;
+
+	/** Summary of the change */
+	const char *summary;
+
+	/** Commit message's body */
+	const char *body;
+
+	/** Author of the change */
+	const git_signature *author;
+} git_diff_format_email_options;
+
+#define GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION 1
+#define GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT {GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION, 0, 1, 1, NULL, NULL, NULL, NULL}
+
+/**
+ * Create an e-mail ready patch from a diff.
+ *
+ * @deprecated git_email_create_from_diff
+ * @see git_email_create_from_diff
+ */
+GIT_EXTERN(int) git_diff_format_email(
+	git_buf *out,
+	git_diff *diff,
+	const git_diff_format_email_options *opts);
+
+/**
+ * Create an e-mail ready patch for a commit.
+ *
+ * @deprecated git_email_create_from_commit
+ * @see git_email_create_from_commit
+ */
+GIT_EXTERN(int) git_diff_commit_as_email(
+	git_buf *out,
+	git_repository *repo,
+	git_commit *commit,
+	size_t patch_no,
+	size_t total_patches,
+	uint32_t flags,
+	const git_diff_options *diff_opts);
+
+/**
+ * Initialize git_diff_format_email_options structure
+ *
+ * Initializes a `git_diff_format_email_options` with default values. Equivalent
+ * to creating an instance with GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT.
+ *
+ * @param opts The `git_blame_options` struct to initialize.
+ * @param version The struct version; pass `GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION`.
+ * @return Zero on success; -1 on failure.
+ */
+GIT_EXTERN(int) git_diff_format_email_options_init(
+	git_diff_format_email_options *opts,
+	unsigned int version);
+
+/**@}*/
+
 /** @name Deprecated Error Functions and Constants
  *
  * These functions and enumeration values are retained for backward

diff --git a/include/git2/diff.h b/include/git2/diff.h
@@ -1376,99 +1376,6 @@ GIT_EXTERN(int) git_diff_stats_to_buf(
  */
 GIT_EXTERN(void) git_diff_stats_free(git_diff_stats *stats);
 
-/**
- * Formatting options for diff e-mail generation
- */
-typedef enum {
-	/** Normal patch, the default */
-	GIT_DIFF_FORMAT_EMAIL_NONE = 0,
-
-	/** Don't insert "[PATCH]" in the subject header*/
-	GIT_DIFF_FORMAT_EMAIL_EXCLUDE_SUBJECT_PATCH_MARKER = (1 << 0),
-
-} git_diff_format_email_flags_t;
-
-/**
- * Options for controlling the formatting of the generated e-mail.
- */
-typedef struct {
-	unsigned int version;
-
-	/** see `git_diff_format_email_flags_t` above */
-	uint32_t flags;
-
-	/** This patch number */
-	size_t patch_no;
-
-	/** Total number of patches in this series */
-	size_t total_patches;
-
-	/** id to use for the commit */
-	const git_oid *id;
-
-	/** Summary of the change */
-	const char *summary;
-
-	/** Commit message's body */
-	const char *body;
-
-	/** Author of the change */
-	const git_signature *author;
-} git_diff_format_email_options;
-
-#define GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION 1
-#define GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT {GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION, 0, 1, 1, NULL, NULL, NULL, NULL}
-
-/**
- * Create an e-mail ready patch from a diff.
- *
- * @param out buffer to store the e-mail patch in
- * @param diff containing the commit
- * @param opts structure with options to influence content and formatting.
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_diff_format_email(
-	git_buf *out,
-	git_diff *diff,
-	const git_diff_format_email_options *opts);
-
-/**
- * Create an e-mail ready patch for a commit.
- *
- * Does not support creating patches for merge commits (yet).
- *
- * @param out buffer to store the e-mail patch in
- * @param repo containing the commit
- * @param commit pointer to up commit
- * @param patch_no patch number of the commit
- * @param total_patches total number of patches in the patch set
- * @param flags determines the formatting of the e-mail
- * @param diff_opts structure with options to influence diff or NULL for defaults.
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_diff_commit_as_email(
-	git_buf *out,
-	git_repository *repo,
-	git_commit *commit,
-	size_t patch_no,
-	size_t total_patches,
-	uint32_t flags,
-	const git_diff_options *diff_opts);
-
-/**
- * Initialize git_diff_format_email_options structure
- *
- * Initializes a `git_diff_format_email_options` with default values. Equivalent
- * to creating an instance with GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT.
- *
- * @param opts The `git_blame_options` struct to initialize.
- * @param version The struct version; pass `GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION`.
- * @return Zero on success; -1 on failure.
- */
-GIT_EXTERN(int) git_diff_format_email_options_init(
-	git_diff_format_email_options *opts,
-	unsigned int version);
-
 /**
  * Patch ID options structure
  *

diff --git a/include/git2/email.h b/include/git2/email.h
@@ -0,0 +1,127 @@
+/*
+ * 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),
+
+	/** Do not perform rename or similarity detection. */
+	GIT_EMAIL_CREATE_NO_RENAMES = (1u << 2),
+} 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;
+
+	/** Options for finding similarities within diffs */
+	git_diff_find_options diff_find_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;
+
+/*
+ * By default, our options include rename detection and binary
+ * diffs to match `git format-patch`.
+ */
+#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_VERSION, GIT_DIFF_SHOW_BINARY, GIT_SUBMODULE_IGNORE_UNSPECIFIED, {NULL,0}, NULL, NULL, NULL, 3 }, \
+	GIT_DIFF_FIND_OPTIONS_INIT \
+}
+
+/**
+ * Create a diff for a commit in mbox format for sending via email.
+ *
+ * @param out buffer to store the e-mail patch in
+ * @param diff the changes to include in the email
+ * @param patch_idx the patch index
+ * @param patch_count the total number of patches that will be included
+ * @param commit_id the commit id for this change
+ * @param summary the commit message for this change
+ * @param body optional text to include above the diffstat
+ * @param author the person who authored this commit
+ * @param opts email creation options
+ */
+GIT_EXTERN(int) git_email_create_from_diff(
+	git_buf *out,
+	git_diff *diff,
+	size_t patch_idx,
+	size_t patch_count,
+	const git_oid *commit_id,
+	const char *summary,
+	const char *body,
+	const git_signature *author,
+	const git_email_create_options *opts);
+
+/**
+ * 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);
+
+GIT_END_DECL
+
+/** @} */
+
+#endif
diff --git a/include/git2/sys/email.h b/include/git2/sys/email.h
@@ -0,0 +1,45 @@
+/*
+ * 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_sys_git_email_h__
+#define INCLUDE_sys_git_email_h__
+
+/**
+ * @file git2/sys/email.h
+ * @brief Advanced git email creation routines
+ * @defgroup git_email Advanced git email creation routines
+ * @ingroup Git
+ * @{
+ */
+GIT_BEGIN_DECL
+
+/**
+ * Create a diff for a commit in mbox format for sending via email.
+ *
+ * @param out buffer to store the e-mail patch in
+ * @param diff the changes to include in the email
+ * @param patch_idx the patch index
+ * @param patch_count the total number of patches that will be included
+ * @param commit_id the commit id for this change
+ * @param summary the commit message for this change
+ * @param body optional text to include above the diffstat
+ * @param author the person who authored this commit
+ * @param opts email creation options
+ */
+GIT_EXTERN(int) git_email_create_from_diff(
+	git_buf *out,
+	git_diff *diff,
+	size_t patch_idx,
+	size_t patch_count,
+	const git_oid *commit_id,
+	const char *summary,
+	const char *body,
+	const git_signature *author,
+	const git_email_create_options *opts);
+
+/** @} */
+GIT_END_DECL
+#endif
diff --git a/src/buffer.c b/src/buffer.c
@@ -600,6 +600,13 @@ void git_buf_shorten(git_buf *buf, size_t amount)
 		git_buf_clear(buf);
 }
 
+void git_buf_truncate_at_char(git_buf *buf, char separator)
+{
+	ssize_t idx = git_buf_find(buf, separator);
+	if (idx >= 0)
+		git_buf_truncate(buf, (size_t)idx);
+}
+
 void git_buf_rtruncate_at_char(git_buf *buf, char separator)
 {
 	ssize_t idx = git_buf_rfind_next(buf, separator);