Memoize result value in Utilities.getremote (#1838)

Utilities.getremote is called when figuring out the URL to methods while
rendering the documentation. A profile of makedocs for Documenters docs
showed that almost a third of the collected samples was inside
getremote, and in particular in the spawned process to git. This patch
memoizes the result of getremote (on a per-source-file basis). This
should give noticeable improvements, since this function is often often
called with the same argument.

(cherry picked from commit 14c1ef2)

CHANGELOG.md

@@ -5,6 +5,7 @@
 * ![Enhancement][badge-enhancement] Documenter can now build draft version of HTML documentation by passing `draft=true` to `makedocs`. Draft mode skips potentially expensive parts of the building process and can be useful to get faster feedback when writing documentation. Draft mode currently skips doctests, `@example`-, `@repl`-, `@eval`-, and `@setup`-blocks. Draft mode can be disabled (or enabled) on a per-page basis by setting `Draft = true` in an `@meta` block. ([#1836][github-1836])
 * ![Enhancement][badge-enhancement] On the HTML search page, pressing enter no longer causes the page to refresh (and therefore does not trigger the slow search index rebuild). ([#1728][github-1728], [#1833][github-1833], [#1834][github-1834])
 * ![Enhancement][badge-enhancement] For the `edit_link` keyword to `HTML()`, Documenter automatically tries to figure out if the remote default branch is `main`, `master`, or something else. It will print a warning if it is unable to reliably determine either `edit_link` or `devbranch` (for `deploydocs`). ([#1827][github-1827], [#1829][github-1829])
+* ![Enhancement][badge-enhancement] Profiling showed that a significant amount of the HTML page build time was due to external `git` commands (used to find remote URLs for docstrings). These results are now cached on a per-source-file basis resulting in faster build times. This is particularly useful when using [LiveServer.jl][liveserver]s functionality for live-updating the docs while writing. ([#1838][github-1838])
 
 ## Version `v0.27.18`
 
@@ -1049,6 +1050,7 @@
 [github-1833]: https://github.com/JuliaDocs/Documenter.jl/pull/1833
 [github-1834]: https://github.com/JuliaDocs/Documenter.jl/pull/1834
 [github-1836]: https://github.com/JuliaDocs/Documenter.jl/pull/1836
+[github-1838]: https://github.com/JuliaDocs/Documenter.jl/pull/1838
 <!-- end of issue link definitions -->
 
 [julia-38079]: https://github.com/JuliaLang/julia/issues/38079
@@ -1060,6 +1062,7 @@
 [documentermarkdown]: https://github.com/JuliaDocs/DocumenterMarkdown.jl
 [json-jl]: https://github.com/JuliaIO/JSON.jl
 [juliamono]: https://cormullion.github.io/pages/2020-07-26-JuliaMono/
+[liveserver]: https://github.com/tlienart/LiveServer.jl
 
 
 [badge-breaking]: https://img.shields.io/badge/BREAKING-red.svg

scripts/changelog.jl

@@ -8,7 +8,7 @@ using CommonMark
 # Configuration:
 
 const LINKREF_EXCEPTIONS = [
-    "json-jl", "juliamono", "documenterlatex", "documentermarkdown",
+    "json-jl", "juliamono", "documenterlatex", "documentermarkdown", "liveserver",
     r"^julia-([0-9]+)$",
     r"^julialangorg-([0-9]+)$",
     r"^badge-([a-z]+)$",

src/Utilities/Utilities.jl

@@ -512,19 +512,17 @@ function url(remote, repo, mod, file, linerange)
     end
 end
 
+const GIT_REMOTE_CACHE = Dict{String,String}()
+
 function getremote(dir::AbstractString)
-    remote =
-        try
-            cd(() -> readchomp(`git config --get remote.origin.url`), dir)
-        catch err
+    return get!(GIT_REMOTE_CACHE, dir) do
+        remote = try
+            readchomp(setenv(`git config --get remote.origin.url`; dir=dir))
+        catch
             ""
         end
-    m = match(LibGit2.GITHUB_REGEX, remote)
-    if m === nothing
-        travis = get(ENV, "TRAVIS_REPO_SLUG", "")
-        isempty(travis) ? "" : travis
-    else
-        m[1]
+        m = match(LibGit2.GITHUB_REGEX, remote)
+        return m === nothing ? get(ENV, "TRAVIS_REPO_SLUG", "") : String(m[1])
     end
 end