[PATCH] pretty: Add "%aU"|"%au" option to output author's username

[PATCH] pretty: Add "%aU"|"%au" option to output author's username

[Prarit Bhargava]

In many projects the number of contributors is low enough that users know
each other and the full email address doesn't need to be displayed.
Displaying only the author's username saves a lot of columns on the screen.
For example displaying "prarit" instead of "prarit@redhat.com" saves 11
columns.

Add a "%aU"|"%au" option that outputs the author's email username.

Also add tests for "%ae" and "%an".

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
---
 Documentation/pretty-formats.txt |  3 +++
 pretty.c                         |  5 +++++
 t/t4202-log.sh                   | 16 ++++++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index b87e2e83e6d0..479a15a8ab12 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -163,6 +163,9 @@ The placeholders are:
 '%ae':: author email
 '%aE':: author email (respecting .mailmap, see linkgit:git-shortlog[1]
 	or linkgit:git-blame[1])
+'%au':: author username
+'%aU':: author username (respecting .mailmap, see linkgit:git-shortlog[1]
+	or linkgit:git-blame[1])
 '%ad':: author date (format respects --date= option)
 '%aD':: author date, RFC2822 style
 '%ar':: author date, relative
diff --git a/pretty.c b/pretty.c
index b32f0369531c..2a5b93022050 100644
--- a/pretty.c
+++ b/pretty.c
@@ -706,6 +706,11 @@ static size_t format_person_part(struct strbuf *sb, char part,
 		strbuf_add(sb, mail, maillen);
 		return placeholder_len;
 	}
+	if (part == 'u' || part == 'U') {	/* username */
+		maillen = strstr(s.mail_begin, "@") - s.mail_begin;
+		strbuf_add(sb, mail, maillen);
+		return placeholder_len;
+	}
 
 	if (!s.date_begin)
 		goto skip;
diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index e803ba402e9e..2fee0c067197 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -1729,4 +1729,20 @@ test_expect_success 'log --end-of-options' '
        test_cmp expect actual
 '
 
+test_expect_success 'log pretty %an %ae %au' '
+	git checkout -b anaeau &&
+	test_commit anaeau_test anaeau_test_file &&
+	git log --pretty="%an" > actual &&
+	git log --pretty="%ae" >> actual &&
+	git log --pretty="%au" >> actual &&
+	git log > full &&
+	name=$(cat full | grep "^Author: " | awk -F "Author: " " { print \$2 } " | awk -F " <" " { print \$1 } ") &&
+	email=$(cat full | grep "^Author: " | awk -F "<" " { print \$2 } " | awk -F ">" " { print \$1 } ") &&
+	username=$(cat full | grep "^Author: " | awk -F "<" " { print \$2 } " | awk -F ">" " { print \$1 } " | awk -F "@" " { print \$1 } " ) &&
+	echo "${name}" > expect &&
+	echo "${email}" >> expect &&
+	echo "${username}" >> expect &&
+	test_cmp expect actual
+'
+
 test_done
-- 
2.21.0

Re: [PATCH] pretty: Add "%aU"|"%au" option to output author's username

[Junio C Hamano]

Prarit Bhargava <prarit@redhat.com> writes:

> Subject: Re: [PATCH] pretty: Add "%aU"|"%au" option to output author's username

Downcase "Add" (see "git shortlog --no-merges -100 master" and
mimick the project convention).

> Add a "%aU"|"%au" option that outputs the author's email username.

Even though I personally do not see the use for it, I agree it would
make sense to have an option to show the local part only where the
e-mail address is shown.  

I do not know if u/U is a good mnemonic; it hints too strongly that
it may come from GIT_{AUTHOR/COMMITTER}_NAME but that is not what
you are doing---isn't there a letter that better conveys that this
is about RFC 2822 local-part (cf. page 16 ieft.org/rfc/rfc2822.txt)?

> diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
> index b87e2e83e6d0..479a15a8ab12 100644
> --- a/Documentation/pretty-formats.txt
> +++ b/Documentation/pretty-formats.txt
> @@ -163,6 +163,9 @@ The placeholders are:
>  '%ae':: author email
>  '%aE':: author email (respecting .mailmap, see linkgit:git-shortlog[1]
>  	or linkgit:git-blame[1])
> +'%au':: author username
> +'%aU':: author username (respecting .mailmap, see linkgit:git-shortlog[1]
> +	or linkgit:git-blame[1])
>  '%ad':: author date (format respects --date= option)
>  '%aD':: author date, RFC2822 style
>  '%ar':: author date, relative

> diff --git a/pretty.c b/pretty.c
> index b32f0369531c..2a5b93022050 100644
> --- a/pretty.c
> +++ b/pretty.c
> @@ -706,6 +706,11 @@ static size_t format_person_part(struct strbuf *sb, char part,
>  		strbuf_add(sb, mail, maillen);
>  		return placeholder_len;
>  	}
> +	if (part == 'u' || part == 'U') {	/* username */
> +		maillen = strstr(s.mail_begin, "@") - s.mail_begin;
> +		strbuf_add(sb, mail, maillen);
> +		return placeholder_len;
> +	}

I think users get %eu and %eU for free with this change, which should
be documented.

Re: [PATCH] pretty: Add "%aU"|"%au" option to output author's username

[brian m. carlson]

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On 2019-10-22 at 23:28:47, Prarit Bhargava wrote:
> In many projects the number of contributors is low enough that users know
> each other and the full email address doesn't need to be displayed.
> Displaying only the author's username saves a lot of columns on the screen.
> For example displaying "prarit" instead of "prarit@redhat.com" saves 11
> columns.
> 
> Add a "%aU"|"%au" option that outputs the author's email username.

I have no position on whether or not this is a useful change.  I don't
think I'll end up using it, but I can imagine cases where it is useful,
such as certain corporate environments.  It would be interesting to see
what others think.

> diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
> index b87e2e83e6d0..479a15a8ab12 100644
> --- a/Documentation/pretty-formats.txt
> +++ b/Documentation/pretty-formats.txt
> @@ -163,6 +163,9 @@ The placeholders are:
>  '%ae':: author email
>  '%aE':: author email (respecting .mailmap, see linkgit:git-shortlog[1]
>  	or linkgit:git-blame[1])
> +'%au':: author username
> +'%aU':: author username (respecting .mailmap, see linkgit:git-shortlog[1]
> +	or linkgit:git-blame[1])

I think we need to actually document what "username" means here.  I
expect you'll have people think that this magically means their
$HOSTING_PLATFORM username, which it is not.

> diff --git a/pretty.c b/pretty.c
> index b32f0369531c..2a5b93022050 100644
> --- a/pretty.c
> +++ b/pretty.c
> @@ -706,6 +706,11 @@ static size_t format_person_part(struct strbuf *sb, char part,
>  		strbuf_add(sb, mail, maillen);
>  		return placeholder_len;
>  	}
> +	if (part == 'u' || part == 'U') {	/* username */
> +		maillen = strstr(s.mail_begin, "@") - s.mail_begin;
> +		strbuf_add(sb, mail, maillen);
> +		return placeholder_len;
> +	}

This branch doesn't appear to do anything different for the mailmap and
non-mailmap cases.  Perhaps adding an additional test that demonstrates
the difference would be a good idea.
-- 
brian m. carlson: Houston, Texas, US
OpenPGP: https://keybase.io/bk2204

[-- Attachment #2: signature.asc --]
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Re: [PATCH] pretty: Add "%aU"|"%au" option to output author's username

[Jeff King]

On Tue, Oct 22, 2019 at 07:28:47PM -0400, Prarit Bhargava wrote:

> In many projects the number of contributors is low enough that users know
> each other and the full email address doesn't need to be displayed.
> Displaying only the author's username saves a lot of columns on the screen.
> For example displaying "prarit" instead of "prarit@redhat.com" saves 11
> columns.
> 
> Add a "%aU"|"%au" option that outputs the author's email username.

Like others, this seems potentially useful even if I probably wouldn't
use it myself. Another more complicated way to think of it would be to
give a list of domains to omit (so if 90% of the committers are
@redhat.com, we can skip that, but the one-off contributor from another
domain gets their fully qualified name.

But that's a lot more complicated. I don't mind doing the easy thing
now, and even if we later grew the more complicated thing, I wouldn't be
sad to still have this easy one as an option.

> --- a/pretty.c
> +++ b/pretty.c
> @@ -706,6 +706,11 @@ static size_t format_person_part(struct strbuf *sb, char part,
>  		strbuf_add(sb, mail, maillen);
>  		return placeholder_len;
>  	}
> +	if (part == 'u' || part == 'U') {	/* username */
> +		maillen = strstr(s.mail_begin, "@") - s.mail_begin;
> +		strbuf_add(sb, mail, maillen);
> +		return placeholder_len;
> +	}

What happens if the email doesn't have an "@"? I think you'd either end
up printing a bunch of extra cruft (because you're not limiting the
search for "@" to the boundaries from split_ident_line) or you'd
crash (if there's no "@" at all, and you'd get a huge maillen).

There's also no need to use the slower strstr() when looking for a
single character. So perhaps:

  const char *at = memchr(mail, '@', maillen);
  if (at)
          maillen = at - mail;
  strbuf_add(sb, mail, maillen);

> +test_expect_success 'log pretty %an %ae %au' '

As others noted, this could cover %aU, too (which is broken; you need to
handle 'U' alongside 'E' and 'N' earlier in format_person_part()).

> +	git checkout -b anaeau &&
> +	test_commit anaeau_test anaeau_test_file &&
> +	git log --pretty="%an" > actual &&
> +	git log --pretty="%ae" >> actual &&
> +	git log --pretty="%au" >> actual &&

Maybe:

  git log --pretty="%an %ae %au"

or

  git log --pretty="%an%n%ae%n%au"

which is shorter and runs more efficiently?

> +	git log > full &&
> +	name=$(cat full | grep "^Author: " | awk -F "Author: " " { print \$2 } " | awk -F " <" " { print \$1 } ") &&
> +	email=$(cat full | grep "^Author: " | awk -F "<" " { print \$2 } " | awk -F ">" " { print \$1 } ") &&
> +	username=$(cat full | grep "^Author: " | awk -F "<" " { print \$2 } " | awk -F ">" " { print \$1 } " | awk -F "@" " { print \$1 } " ) &&
> +	echo "${name}" > expect &&
> +	echo "${email}" >> expect &&
> +	echo "${username}" >> expect &&

These values come from our hard-coded test setup, so it would be more
readable to just expect those:

  {
	echo "$GIT_AUTHOR_NAME" &&
	echo "$GIT_AUTHOR_EMAIL" &&
	echo "$GIT_AUTHOR_EMAIL" | sed "s/@.*//"
  } >expect

For the last one, also I wouldn't be upset to see test-lib.sh do
something like:

  TEST_AUTHOR_USERNAME=author
  TEST_AUTHOR_DOMAIN=example.com
  GIT_AUTHOR_NAME=$TEST_AUTHOR_USERNAME@$TEST_AUTHOR_DOMAIN

to let tests like this pick out the individual values if they want.

-Peff

Re: [PATCH] pretty: Add "%aU"|"%au" option to output author's username

[Prarit Bhargava]

On 10/22/19 7:46 PM, Junio C Hamano wrote:
> Prarit Bhargava <prarit@redhat.com> writes:
> 
>> Subject: Re: [PATCH] pretty: Add "%aU"|"%au" option to output author's username
> 
> Downcase "Add" (see "git shortlog --no-merges -100 master" and
> mimick the project convention).

I'll fix that.

> 
>> Add a "%aU"|"%au" option that outputs the author's email username.
> 
> Even though I personally do not see the use for it, I agree it would
> make sense to have an option to show the local part only where the
> e-mail address is shown.  
> 
> I do not know if u/U is a good mnemonic; it hints too strongly that
> it may come from GIT_{AUTHOR/COMMITTER}_NAME but that is not what
> you are doing---isn't there a letter that better conveys that this
> is about RFC 2822 local-part (cf. page 16 ieft.org/rfc/rfc2822.txt)?

I'll go with "l" and "L" for local-part as defined on page 16.  I will also
include a comment in braces that says (the portion of the email address
preceding the '@' symbol)".  Admittedly that doesn't convey the meaning of the
mailbox concept of the email address it does tell a user what is going to be output.

> 
>> diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
>> index b87e2e83e6d0..479a15a8ab12 100644
>> --- a/Documentation/pretty-formats.txt
>> +++ b/Documentation/pretty-formats.txt
>> @@ -163,6 +163,9 @@ The placeholders are:
>>  '%ae':: author email
>>  '%aE':: author email (respecting .mailmap, see linkgit:git-shortlog[1]
>>  	or linkgit:git-blame[1])
>> +'%au':: author username
>> +'%aU':: author username (respecting .mailmap, see linkgit:git-shortlog[1]
>> +	or linkgit:git-blame[1])
>>  '%ad':: author date (format respects --date= option)
>>  '%aD':: author date, RFC2822 style
>>  '%ar':: author date, relative
> 
>> diff --git a/pretty.c b/pretty.c
>> index b32f0369531c..2a5b93022050 100644
>> --- a/pretty.c
>> +++ b/pretty.c
>> @@ -706,6 +706,11 @@ static size_t format_person_part(struct strbuf *sb, char part,
>>  		strbuf_add(sb, mail, maillen);
>>  		return placeholder_len;
>>  	}
>> +	if (part == 'u' || part == 'U') {	/* username */
>> +		maillen = strstr(s.mail_begin, "@") - s.mail_begin;
>> +		strbuf_add(sb, mail, maillen);
>> +		return placeholder_len;
>> +	}
> 
> I think users get %eu and %eU for free with this change, which should
> be documented.
> 

Did you mean %cu and %cU?  Or am I missing something with "%e"?

P.

Re: [PATCH] pretty: Add "%aU"|"%au" option to output author's username

[Prarit Bhargava]

On 10/22/19 7:48 PM, brian m. carlson wrote:
> On 2019-10-22 at 23:28:47, Prarit Bhargava wrote:
>> In many projects the number of contributors is low enough that users know
>> each other and the full email address doesn't need to be displayed.
>> Displaying only the author's username saves a lot of columns on the screen.
>> For example displaying "prarit" instead of "prarit@redhat.com" saves 11
>> columns.
>>
>> Add a "%aU"|"%au" option that outputs the author's email username.
> 
> I have no position on whether or not this is a useful change.  I don't
> think I'll end up using it, but I can imagine cases where it is useful,
> such as certain corporate environments.  It would be interesting to see
> what others think.
> 
>> diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
>> index b87e2e83e6d0..479a15a8ab12 100644
>> --- a/Documentation/pretty-formats.txt
>> +++ b/Documentation/pretty-formats.txt
>> @@ -163,6 +163,9 @@ The placeholders are:
>>  '%ae':: author email
>>  '%aE':: author email (respecting .mailmap, see linkgit:git-shortlog[1]
>>  	or linkgit:git-blame[1])
>> +'%au':: author username
>> +'%aU':: author username (respecting .mailmap, see linkgit:git-shortlog[1]
>> +	or linkgit:git-blame[1])
> 
> I think we need to actually document what "username" means here.  I
> expect you'll have people think that this magically means their
> $HOSTING_PLATFORM username, which it is not.
> 

Based on Junio's input, I'm going to change the option to "al" and "aL" where L
means "local-part" as defined by the rfc2822.txt specification, and include a
comment that says "(the portion of the email address preceding the '@' symbol)".
 Admittedly that doesn't convey the meaning of the mailbox concept of the email
address it does tell a user what is going to be output.


>> diff --git a/pretty.c b/pretty.c
>> index b32f0369531c..2a5b93022050 100644
>> --- a/pretty.c
>> +++ b/pretty.c
>> @@ -706,6 +706,11 @@ static size_t format_person_part(struct strbuf *sb, char part,
>>  		strbuf_add(sb, mail, maillen);
>>  		return placeholder_len;
>>  	}
>> +	if (part == 'u' || part == 'U') {	/* username */
>> +		maillen = strstr(s.mail_begin, "@") - s.mail_begin;
>> +		strbuf_add(sb, mail, maillen);
>> +		return placeholder_len;
>> +	}
> 
> This branch doesn't appear to do anything different for the mailmap and
> non-mailmap cases.  Perhaps adding an additional test that demonstrates
> the difference would be a good idea.
> 

Thanks for the suggestion.  I'll look into it for v2.

P.

Re: [PATCH] pretty: Add "%aU"|"%au" option to output author's username

[Prarit Bhargava]

On 10/23/19 1:02 AM, Jeff King wrote:
> On Tue, Oct 22, 2019 at 07:28:47PM -0400, Prarit Bhargava wrote:
> 
>> In many projects the number of contributors is low enough that users know
>> each other and the full email address doesn't need to be displayed.
>> Displaying only the author's username saves a lot of columns on the screen.
>> For example displaying "prarit" instead of "prarit@redhat.com" saves 11
>> columns.
>>
>> Add a "%aU"|"%au" option that outputs the author's email username.
> 
> Like others, this seems potentially useful even if I probably wouldn't
> use it myself. Another more complicated way to think of it would be to
> give a list of domains to omit (so if 90% of the committers are
> @redhat.com, we can skip that, but the one-off contributor from another
> domain gets their fully qualified name.>
> But that's a lot more complicated. I don't mind doing the easy thing
> now, and even if we later grew the more complicated thing, I wouldn't be
> sad to still have this easy one as an option.

FWIW, I went through the exact same thought process as you did and came to the
same conclusion.

> 
>> --- a/pretty.c
>> +++ b/pretty.c
>> @@ -706,6 +706,11 @@ static size_t format_person_part(struct strbuf *sb, char part,
>>  		strbuf_add(sb, mail, maillen);
>>  		return placeholder_len;
>>  	}
>> +	if (part == 'u' || part == 'U') {	/* username */
>> +		maillen = strstr(s.mail_begin, "@") - s.mail_begin;
>> +		strbuf_add(sb, mail, maillen);
>> +		return placeholder_len;
>> +	}
> 
> What happens if the email doesn't have an "@"? I think you'd either end
> up printing a bunch of extra cruft (because you're not limiting the
> search for "@" to the boundaries from split_ident_line) or you'd
> crash (if there's no "@" at all, and you'd get a huge maillen).
> 
> There's also no need to use the slower strstr() when looking for a
> single character. So perhaps:
> 
>   const char *at = memchr(mail, '@', maillen);
>   if (at)
>           maillen = at - mail;
>   strbuf_add(sb, mail, maillen);

TBH I had assumed that the email address was RFC2822 compliant.  Thanks for the
code.  I've incorporated it into v2.

> 
>> +test_expect_success 'log pretty %an %ae %au' '
> 
> As others noted, this could cover %aU, too (which is broken; you need to
> handle 'U' alongside 'E' and 'N' earlier in format_person_part()).

Whups.  Thanks for the pointer.  Also fixed in v2.

> 
>> +	git checkout -b anaeau &&
>> +	test_commit anaeau_test anaeau_test_file &&
>> +	git log --pretty="%an" > actual &&
>> +	git log --pretty="%ae" >> actual &&
>> +	git log --pretty="%au" >> actual &&
> 
> Maybe:
> 
>   git log --pretty="%an %ae %au"
> 
> or
> 
>   git log --pretty="%an%n%ae%n%au"
> 
> which is shorter and runs more efficiently?
> 
>> +	git log > full &&
>> +	name=$(cat full | grep "^Author: " | awk -F "Author: " " { print \$2 } " | awk -F " <" " { print \$1 } ") &&
>> +	email=$(cat full | grep "^Author: " | awk -F "<" " { print \$2 } " | awk -F ">" " { print \$1 } ") &&
>> +	username=$(cat full | grep "^Author: " | awk -F "<" " { print \$2 } " | awk -F ">" " { print \$1 } " | awk -F "@" " { print \$1 } " ) &&
>> +	echo "${name}" > expect &&
>> +	echo "${email}" >> expect &&
>> +	echo "${username}" >> expect &&
> 
> These values come from our hard-coded test setup, so it would be more
> readable to just expect those:
> 
>   {
> 	echo "$GIT_AUTHOR_NAME" &&
> 	echo "$GIT_AUTHOR_EMAIL" &&
> 	echo "$GIT_AUTHOR_EMAIL" | sed "s/@.*//"
>   } >expect

Added to v2 (along with Brian's suggestion to test %aE, %aN, and %aL).

> 
> For the last one, also I wouldn't be upset to see test-lib.sh do
> something like:
> 
>   TEST_AUTHOR_USERNAME=author
>   TEST_AUTHOR_DOMAIN=example.com
>   GIT_AUTHOR_NAME=$TEST_AUTHOR_USERNAME@$TEST_AUTHOR_DOMAIN

I like this suggestion a lot.  I'm incorporating into v2 as well as similar
changes for the COMMITTER fields.

P.

> 
> to let tests like this pick out the individual values if they want.
> 
> -Peff
> 

Re: [PATCH] pretty: Add "%aU"|"%au" option to output author's username

[Junio C Hamano]

"brian m. carlson" <sandals@crustytoothpaste.net> writes:

>> +	if (part == 'u' || part == 'U') {	/* username */
>> +		maillen = strstr(s.mail_begin, "@") - s.mail_begin;
>> +		strbuf_add(sb, mail, maillen);
>> +		return placeholder_len;
>> +	}
>
> This branch doesn't appear to do anything different for the mailmap and
> non-mailmap cases.  Perhaps adding an additional test that demonstrates
> the difference would be a good idea.

Yes, and the bug that would be exposed is the lack of call to
mailmap.

Perhaps along this line (I may have off-by-one or two tho)?

 pretty.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/pretty.c b/pretty.c
index e4ed14effe..4b76d022c6 100644
--- a/pretty.c
+++ b/pretty.c
@@ -696,15 +696,27 @@ static size_t format_person_part(struct strbuf *sb, char part,
 	mail = s.mail_begin;
 	maillen = s.mail_end - s.mail_begin;
 
-	if (part == 'N' || part == 'E') /* mailmap lookup */
+	if (part == 'N' || part == 'E' || part == 'L') /* mailmap lookup */
 		mailmap_name(&mail, &maillen, &name, &namelen);
-	if (part == 'n' || part == 'N') {	/* name */
+
+	switch (part) {
+	case 'n': case 'N':
 		strbuf_add(sb, name, namelen);
 		return placeholder_len;
-	}
-	if (part == 'e' || part == 'E') {	/* email */
+	case 'l': case 'L':
+		{
+			const char *at = memchr(mail, '@', maillen);
+			if (at) {
+				maillen -= at - mail + 1;
+				mail = at + 1;
+			}
+		}
+		/* fall through */
+	case 'e': case 'E': 
 		strbuf_add(sb, mail, maillen);
 		return placeholder_len;
+	default:
+		break;
 	}
 
 	if (!s.date_begin)

Re: [PATCH] pretty: Add "%aU"|"%au" option to output author's username

[Prarit Bhargava]

On 10/23/19 10:29 PM, Junio C Hamano wrote:
> "brian m. carlson" <sandals@crustytoothpaste.net> writes:
> 
>>> +	if (part == 'u' || part == 'U') {	/* username */
>>> +		maillen = strstr(s.mail_begin, "@") - s.mail_begin;
>>> +		strbuf_add(sb, mail, maillen);
>>> +		return placeholder_len;
>>> +	}
>>
>> This branch doesn't appear to do anything different for the mailmap and
>> non-mailmap cases.  Perhaps adding an additional test that demonstrates
>> the difference would be a good idea.
> 
> Yes, and the bug that would be exposed is the lack of call to
> mailmap.
> 
> Perhaps along this line (I may have off-by-one or two tho)?
> 
>  pretty.c | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/pretty.c b/pretty.c
> index e4ed14effe..4b76d022c6 100644
> --- a/pretty.c
> +++ b/pretty.c
> @@ -696,15 +696,27 @@ static size_t format_person_part(struct strbuf *sb, char part,
>  	mail = s.mail_begin;
>  	maillen = s.mail_end - s.mail_begin;
>  
> -	if (part == 'N' || part == 'E') /* mailmap lookup */
> +	if (part == 'N' || part == 'E' || part == 'L') /* mailmap lookup */
>  		mailmap_name(&mail, &maillen, &name, &namelen);
> -	if (part == 'n' || part == 'N') {	/* name */
> +
> +	switch (part) {
> +	case 'n': case 'N':
>  		strbuf_add(sb, name, namelen);
>  		return placeholder_len;
> -	}
> -	if (part == 'e' || part == 'E') {	/* email */
> +	case 'l': case 'L':
> +		{
> +			const char *at = memchr(mail, '@', maillen);
> +			if (at) {
> +				maillen -= at - mail + 1;
> +				mail = at + 1;

^^^  If the mail is 'prarit@redhat.com' the output of these lines is

	maillen = maillen - at - mail - 1

	which is (16 - [6] - 1) = 9.
	
	and mail = at + 1 points to "redhat.com"

This is the reverse of what we want.  IMO I suggest (sorry for the
cut-and-paste) which keeps the code easy to read.

diff --git a/pretty.c b/pretty.c
index b32f0369531c..93eb6e837071 100644
--- a/pretty.c
+++ b/pretty.c
@@ -696,7 +696,7 @@ static size_t format_person_part(struct strbuf *sb, char par
t,
        mail = s.mail_begin;
        maillen = s.mail_end - s.mail_begin;

-       if (part == 'N' || part == 'E') /* mailmap lookup */
+       if (part == 'N' || part == 'E' || part == 'L') /* mailmap lookup */
                mailmap_name(&mail, &maillen, &name, &namelen);
        if (part == 'n' || part == 'N') {       /* name */
                strbuf_add(sb, name, namelen);
@@ -706,6 +706,13 @@ static size_t format_person_part(struct strbuf *sb, char pa
rt,
                strbuf_add(sb, mail, maillen);
                return placeholder_len;
        }
+       if (part == 'l' || part == 'L') {       /* local-part */
+               const char *at = memchr(mail, '@', maillen);
+               if (at)
+                       maillen = at - mail;
+               strbuf_add(sb, mail, maillen);
+               return placeholder_len;
+       }

        if (!s.date_begin)

Let me submit a v2 with all the suggested changes so that you can review my work
so far.  We can continue the discussion there.

P.

> +			}

> +		}
> +		/* fall through */
> +	case 'e': case 'E': 
>  		strbuf_add(sb, mail, maillen);
>  		return placeholder_len;
> +	default:
> +		break;
>  	}
>  
>  	if (!s.date_begin)
>