[JENKINS-75162] Fix fragment identifiers to plugins.jenkins.io content (#1711)

The previous fragment identifiers in the documentation links no longer
exist in the plugins.jenkins.io page content.  Use fragment identifiers
that exist so that a click of the link takes the reader to the correct
location in the page content.

Partial fix of https://issues.jenkins.io/browse/JENKINS-75162

Author: MarkEWaite

README.adoc

@@ -294,7 +294,7 @@ Other credential types will not work with the ssh protocol.
 To minimize the delay between a push and a build, configure the remote repository to use a Webhook to notify Jenkins of changes to the repository.
 Refer to webhook documentation for your repository:
 
-* link:https://plugins.jenkins.io/github#GitHubPlugin-GitHubhooktriggerforGITScmpolling[GitHub]
+* link:https://plugins.jenkins.io/github/#plugin-content-github-hook-trigger-for-gitscm-polling[GitHub]
 * link:https://plugins.jenkins.io/bitbucket[Bitbucket]
 * link:https://plugins.jenkins.io/gitlab-branch-source[GitLab]
 * link:https://github.com/jenkinsci/gitea-plugin/blob/master/docs/README.md[Gitea]
@@ -364,7 +364,7 @@ hudson.plugins.git.GitStatus.NOTIFY_COMMIT_ACCESS_CONTROL='disabled-for-polling'
 [#enabling-jgit]
 === Enabling JGit
 
-See the link:https://plugins.jenkins.io/git-client/#enabling-jgit[git client plugin documentation] for instructions to enable JGit.
+See the link:https://plugins.jenkins.io/git-client/#plugin-content-enabling-jgit[git client plugin documentation] for instructions to enable JGit.
 JGit becomes available throughout Jenkins once it has been enabled.
 
 [#global-configuration]

src/main/java/hudson/plugins/git/GitSCM.java

@@ -1165,7 +1165,7 @@ public EnvVars getEnvironment() {
         buildData.saveBuild(revToBuild);
 
         if (buildData.getBuildsByBranchName().size() >= 100) {
-            log.println("JENKINS-19022: warning: possible memory leak due to Git plugin usage; see: https://plugins.jenkins.io/git/#remove-git-plugin-buildsbybranch-builddata-script");
+            log.println("JENKINS-19022: warning: possible memory leak due to Git plugin usage; see: https://plugins.jenkins.io/git/#plugin-content-remove-git-plugin-buildsbybranch-builddata-script");
         }
         boolean checkForMultipleRevisions = true;
         BuildSingleRevisionOnly ext = extensions.get(BuildSingleRevisionOnly.class);

src/main/resources/hudson/plugins/git/GitSCM/help.html

@@ -41,7 +41,7 @@
     </p>
     <p>
     The <code>checkout</code> step can be used in many cases where the <code>git</code> step cannot be used.
-    Refer to the <a href="https://plugins.jenkins.io/git#extensions">git plugin documentation</a> for detailed descriptions of options available to the checkout step.
+    Refer to the <a href="https://plugins.jenkins.io/git/#plugin-content-extensions">git plugin documentation</a> for detailed descriptions of options available to the checkout step.
     For example, the <code>checkout</code> step supports:
     <ul>
       <li>SHA-1 checkout</li>

src/main/resources/jenkins/plugins/git/GitStep/help.html

@@ -34,7 +34,7 @@
     </p>
     <p>
     The <code>checkout</code> step can be used in many cases where the <code>git</code> step cannot be used.
-    Refer to the <a href="https://plugins.jenkins.io/git#extensions">git plugin documentation</a> for detailed descriptions of options available to the checkout step.
+    Refer to the <a href="https://plugins.jenkins.io/git/#plugin-content-extensions">git plugin documentation</a> for detailed descriptions of options available to the checkout step.
     For example, the <code>git</code> step does <strong>not</strong> support:
     <ul>
       <li>SHA-1 checkout</li>