Re: [PATCH 3/8] merge-ort: record the reason that we want a rename for a directory

[Derrick Stolee <stolee@gmail.com>]

On 3/13/2021 5:22 PM, Elijah Newren via GitGitGadget wrote:
> From: Elijah Newren <newren@gmail.com>
> 
> When one side of history renames a directory, and the other side of
> history added files to the old directory, directory rename detection is
> used to warn about the location of the added files so the user can
> move them to the old directory or keep them with the new one.
> 
> This sets up three different types of directories:
>   * directories that had new files added to them
>   * directories underneath a directory that had new files added to them
>   * directories where no new files were added to it or any leading path
> 
> Save this information in dirs_removed; the next several commits will
> make use of this information.
...
> +/* dir_rename_relevance: the reason we want rename information for a dir */
> +enum dir_rename_relevance {
> +	NOT_RELEVANT = 0,
> +	RELEVANT_FOR_ANCESTOR = 1,
> +	RELEVANT_FOR_SELF = 2
> +};

Is this potentially a flag list? It's hard to tell because we don't
have another item (3 or 4?).

>  		unsigned sides = (0x07 - dirmask)/2;
> +		unsigned relevance = (renames->dir_rename_mask == 0x07) ?
> +					RELEVANT_FOR_ANCESTOR : NOT_RELEVANT;
> +		/*
> +		 * Record relevance of this directory.  However, note that
> +		 * when collect_merge_info_callback() recurses into this
> +		 * directory and calls collect_rename_info() on paths
> +		 * within that directory, if we find a path that was added
> +		 * to this directory on the other side of history, we will
> +		 * upgrade this value to RELEVANT_FOR_SELF; see below.
> +		 */

This comment seems to imply that RELEVANT_FOR_SELF is "more important"
than RELEVANT_FOR_ANCESTOR, so the value will just be changed (not a
flag).

> +	/*
> +	 * Here's the block that potentially upgrades to RELEVANT_FOR_SELF.
> +	 * When we run across a file added to a directory.  In such a case,
> +	 * find the directory of the file and upgrade its relevance.
> +	 */
> +	if (renames->dir_rename_mask == 0x07 &&
> +	    (filemask == 2 || filemask == 4)) {
> +		/*
> +		 * Need directory rename for parent directory on other side
> +		 * of history from added file.  Thus
> +		 *    side = (~filemask & 0x06) >> 1
> +		 * or
> +		 *    side = 3 - (filemask/2).
> +		 */
> +		unsigned side = 3 - (filemask >> 1);
> +		strintmap_set(&renames->dirs_removed[side], dirname,
> +			      RELEVANT_FOR_SELF);

Yes, using "RELEVANT_FOR_SELF" here, not "relevance | RELEVANT_FOR_SELF".
OK. This should make the later consumers simpler.

Thanks,
-Stolee