Porting self-hosted Wordpress to HTTPS: mixed content

[jsha]

When moving a self-hosted Wordpress blog from HTTP to HTTPS (by editing the site URL at /wp-admin/options-general.php), I run into trouble because image links embedded in existing posts still point to HTTP, even though those images are hosted by my Wordpress blog and now support HTTPS.

It would be great if Wordpress could automatically rewrite images in existing posts when site URL is changed to HTTPS.

[joemcgill]

Related #15928

[SergeyBiryukov]

#28521 would resolve this.

[thomaswm]

Related: #33691

[johnbillion]

#33691 was marked as a duplicate.

[thomaswm]

Replace local HTTP URLs in post content using a filter

[thomaswm]

Send "Upgrade Insecure Requests" HTTP header

[thomaswm]

I've uploaded two different patches:

• 29727.diff​ is a nearly exact copy of @wonderboymusic's patch on #28521. It replaces local non-HTTPS URLs using a filter.
• 29727.2.diff​ sends an ​Upgrade Insecure Requests HTTP header when the page is requested through HTTPS. This was suggested in ​a comment on make/core.