many: allow for multiple documentations for a Unit

Change internal.Unit.Documentation from a single
internal.Documentation to a slice, so that a Unit can have doc for
multiple build contexts.

However, don't use this ability yet: fetch takes only the first
build context it finds, postgres inserts only the first, frontend
renders only the first, etc.

For golang/go#37232

Change-Id: I17fd1ff2378e0862c029c8077057c207001f6136
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/288217
Trust: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Julie Qiu <julie@golang.org>
Reviewed-by: Jamal Carvalho <jamal@golang.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/internal/postgres/insert_module.go b/internal/postgres/insert_module.go
index f629187e..a241fc1f 100644
--- a/internal/postgres/insert_module.go
+++ b/internal/postgres/insert_module.go
@@ -328,10 +328,14 @@ func (pdb *DB) insertUnits(ctx context.Context, db *database.DB, m *internal.Mod
 		if u.Readme != nil {
 			pathToReadme[u.Path] = u.Readme
 		}
-		if u.Documentation != nil && u.Documentation.Source == nil {
+		if u.Documentation != nil && u.Documentation[0] != nil && u.Documentation[0].Source == nil {
 			return fmt.Errorf("insertUnits: unit %q missing source files", u.Path)
 		}
-		pathToDoc[u.Path] = u.Documentation
+		if u.Documentation == nil {
+			pathToDoc[u.Path] = nil
+		} else {
+			pathToDoc[u.Path] = u.Documentation[0]
+		}
 		if len(u.Imports) > 0 {
 			pathToImports[u.Path] = u.Imports
 		}