From: Derrick Stolee <stolee@gmail.com>
Date: Thu, 27 Dec 2018 13:20:32 GMT
Subject: Re: [PATCH] log: add %S option (like --source) to log --format
Message-ID: <5dfd92d1-2e87-3006-1630-a33794b6066b@gmail.com>
In-Reply-To: <20181219083305.2500-1-issac.trotts@gmail.com>

On 12/19/2018 3:33 AM, issac.trotts@gmail.com wrote:
> From: Issac Trotts <issac.trotts@gmail.com>
>
> Make it possible to write for example
>
>          git log --format="%H,%S"
>
> where the %S at the end is a new placeholder that prints out the ref
> (tag/branch) for each commit.
>
> Using %d might seem like an alternative but it only shows the ref for the last
> commit in the branch.
>
> Signed-off-by: Issac Trotts <issactrotts@google.com>
>
> ---
>
> This change is based on a question from Stack Overflow:
> https://stackoverflow.com/questions/12712775/git-get-source-information-in-format
> ---
>   Documentation/pretty-formats.txt |  2 ++
>   builtin/log.c                    |  2 +-
>   log-tree.c                       |  1 +
>   pretty.c                         | 15 ++++++++++
>   pretty.h                         |  1 +
>   t/t4205-log-pretty-formats.sh    | 50 ++++++++++++++++++++++++++++++++
>   6 files changed, 70 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
> index 417b638cd..de6953108 100644
> --- a/Documentation/pretty-formats.txt
> +++ b/Documentation/pretty-formats.txt
> @@ -134,6 +134,8 @@ The placeholders are:
>   - '%cI': committer date, strict ISO 8601 format
>   - '%d': ref names, like the --decorate option of linkgit:git-log[1]
>   - '%D': ref names without the " (", ")" wrapping.
> +- '%S': ref name given on the command line by which the commit was reached
> +  (like `git log --source`), only works with `git log`

This "only works with `git log`" made me think about what would happen 
with `git rev-list --pretty=format:"%h %S"` and the answer (on my 
machine) was a segfault.

>   - '%e': encoding
>   - '%s': subject
>   - '%f': sanitized subject line, suitable for a filename
> diff --git a/builtin/log.c b/builtin/log.c
> index e8e51068b..be3025657 100644
> --- a/builtin/log.c
> +++ b/builtin/log.c
> @@ -203,7 +203,7 @@ static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
>   	    rev->diffopt.filter || rev->diffopt.flags.follow_renames)
>   		rev->always_show_header = 0;
>   
> -	if (source) {
> +	if (source || (rev->pretty_given && (rev->commit_format == CMIT_FMT_USERFORMAT) && w.source)) {
>   		init_revision_sources(&revision_sources);
>   		rev->sources = &revision_sources;
>   	}

Likely, you'll want to duplicate this initialization in the revision 
machinery. Keep this one in builtin/log.c as it was before, but add 
something like this initialization to setup_revisions(). Add a test for 
rev-list.

[snip]

> @@ -1194,6 +1195,17 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
>   		load_ref_decorations(NULL, DECORATE_SHORT_REFS);
>   		format_decorations_extended(sb, commit, c->auto_color, "", ", ", "");
>   		return 1;
> +	case 'S':		/* tag/branch like --source */
> +		if (c->pretty_ctx->rev->sources == NULL) {
Use "if (!c->pretty_ctx->rev->sources".
> +			return 0;
> +		}
> +		slot = revision_sources_at(c->pretty_ctx->rev->sources, commit);
> +		if (slot && *slot) {
I'm not sure this check for 'slot' being non-null is necessary, as we 
would already get a failure in the commit-slab code (for 
revision_sources_at()) if the slab is not initialized.
> +			strbuf_addstr(sb, *slot);
> +			return 1;
> +		} else {
> +			die(_("failed to get info for %%S"));

Here, you die() when you fail to get a slot but above you return 0 when 
the sources are not initialized.

I don't see another use of die() in this method. Is that the right way 
to handle failure here? (I'm legitimately asking because I have 
over-used 'die()' in the past and am still unclear on when it is 
appropriate.)

>   '
>   
> +test_expect_success 'set up %S tests' '
> +	git checkout --orphan source-a &&
> +	test_commit one &&
> +	test_commit two &&
> +	git checkout -b source-b HEAD^ &&
> +	test_commit three
> +'
> +
> +test_expect_success 'log --format=%S paints branch names' '
> +	cat >expect <<-\EOF &&
> +	source-b
> +	source-a
> +	source-b
> +	EOF
> +	git log --format=%S source-a source-b >actual &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'log --format=%S paints tag names' '
> +	git tag -m tagged source-tag &&
> +	cat >expect <<-\EOF &&
> +	source-tag
> +	source-a
> +	source-tag
> +	EOF
> +	git log --format=%S source-tag source-a >actual &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'log --format=%S paints symmetric ranges' '
> +	cat >expect <<-\EOF &&
> +	source-b
> +	source-a
> +	EOF
> +	git log --format=%S source-a...source-b >actual &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success '%S in git log --format works with other placeholders (part 1)' '
> +	git log --format="source-b %h" source-b >expect &&
> +	git log --format="%S %h" source-b >actual &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success '%S in git log --format works with other placeholders (part 2)' '
> +	git log --format="%h source-b" source-b >expect &&
> +	git log --format="%h %S" source-b >actual &&
> +	test_cmp expect actual
> +'
> +
>   test_done

Please also add a simple test to t6006-rev-list-format.sh.

Thanks,

-Stolee